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A Close Look at Modern Keyboard/Video/Mouse Switching by

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1. 1280 H XGA Uniform Resolution Map measured CRT monitors cannot display much bet ter than 1600 x 1280 resolution due to electrome chanical limitations in the technology There are now quite a few video driver cards that support 1600 x 1280 or 1600 x 1200 resolution though this high density is generally used only for specialized graphics and video production effects work A few new monitors are very much wider than they are tall the HDTV or High Definition Television format has pushed this along and they may go to 1920 x 1200 resolution though pixel sharpness is hard Page 29 to preserve near the outer reaches of the screen It takes a special video card to be able to drive such wide monitors and these cards are now mar keted Existing KVMS systems generally were not designed for the kind of bandwidth necessary to transfer this exceptionally high resolution video though a few special purpose KVM switches can handle it VESA Video Electronics Standards Association DDC Display Data Channel video cards are built to support a different video standard even though the connectors used are the same as VGA VGA only needs 10 of the 15 pins in its HDD 15 connector VESA DDC uses the additional conductors and pins to convey the DDC serial data data clock a reserved line and 5V power If your computer uses a VESA video adapter
2. cc DE e NTSC Video is Not Optimum for Computers o eee eee eens 31 Other KVMS Factors c c ccc eee ee ee eee nen e eee eee nnnes 32 e Operating System Considerations c c 32 e Computer Hardware Considerations c 32 Methods Ol SWEN 6 05 0 donee bt 6 eaonoe 66S Sod R ESERE S HCE R hese 3 0 6 H es 33 Other Issues 10 CONSICCL 5 a 24 2 aaeg one bane aE a and ens Bae Sa Ea Gb Gone aen ee ig 34 Multi Console KVMS Systems The New Standard ccc 35 e The Explosion in Multi Console Switching c c 35 s ArCHIECINNS 2 Aon oe oe ed oo ee ee eee et ae RAVA ee i ee ee ee eS 35 Physical Considerati0Ns 44 0van262 iea ne seen bo Ghee h ane yee he 2 hh bate kee 40 PAO SUpPOLE a asehicevneuned boone rit EER heehee 465 EET Md us T red Hoe Erde a le 40 e Controlling and Tracking Usage in the KVM Switch System cee eee 4 e Emulation Services 3244 d6urcee td eat rede senvesctetunae des euvegeeleuededes unaceess 41 Capacity and Sealability gt sza eum eie mene 16 shee E a eee oa eee Gas he es ee ee ee 42 e Extending the Distance Local and Long Distance c c 43 Dollar Factors Obvious and Hidden 4 4cuaseuoaee enews yada een e eae oe eee pe nano 46 KVMS Dilecl C0015215 32 auie 0 6 36 d 126 6 16 49 18 380 161 ones ed Sees eE 46 l o e e eee A E E E E E EE E
3. 6 600 750 gt N Q D O S 600 T O 450 300 7 4 P 150 a l ES DA Wh 12 5 h kW 0 Wh Since popular multi console K V M switches often have many more CPUs to a few monitors the dollars saved on power may be significantly higher than those shown here greater than 7 1 ratio Because an operator can access data and exam ine system status with the touch of a finger instead of standing up and walking around to locate the desired monitor and keyboard productivity increas es measurably If you re the operator you will real ly appreciate how much more relaxed you feel at the end of the day You will save a tremendous amount of physical space by using KVMS Particularly as you add serv ers for burgeoning web servers e mail systems fax servers etc you will appreciate the ability to do so without having to provide space for more monitors and keyboards A 50 reduction of floor space is typical when using KVMS and you can get down to as little as 25 of the original floor space if you combine specialized computer racking systems with KVMS Saving space certainly matters and related to that is a reduction in clutter With fewer compo nents physically scattered around the data center or lab it is easier to maintain the remaining equip ment It becomes far less likely that a stashed key board will slip off its precarious perch on an over crowded desk And there will be far less cost asso
4. 200 ft 200 ft Because KVMS lets you use far fewer monitors your monthly power bills will be much lower The typical 17 inch VGA color monitor for example draws about 1 3 amps or 150 watts of power With a typical KVMS controlling 8 computers from a single monitor you reduce the monitor count by 82 In a server room or lab operating around the clock 8 monitors would use 28 8 kilowatt hours kWh per day whereas the single monitor would use just 3 6 kWh per day That 25 2 kWh saved each day amounts to about 9 200 kWh annually A typical California small business Electric bill runs from 10 to 15 per kWh That calculates to be from 920 to 1 380 a year saved in direct electrical consumption but you actually save a lot more First larger systems will typically have more than 8 CPUs per monitor so the numbers improve there In addition you save in air conditioning costs because you don t have to remove the BTUs British Thermal Units or heat generated by those eliminated monitors That same 17 monitor which draws 150 watts generates about 500 BTUs To prevent heat build up about 150 watts of air con ditioning is required so the annual HVAC heating ventilation air conditioning power savings for this 8 1 KVMS setup will be another 9 200 kWh which saves you another 920 to 1 380 annually Green monitors that shut themselve down would use less power so your savings would be less but larger monitors now
5. The digital representation of the color may be fed directly to the monitor for interpretation and often is with flat panel displays but more often the video driver card converts it to a modulated analog signal 1 e one continuously varying in volt age rather than defined by numbers and this analog signal goes to the monitor Digital Video for PCs Early PC monitors utilized TTL signals Transistor Transistor Logic to convey video from the display adapter card to the monitor These are 5 volt digital signals with the video intensity defined by a numerical value The TTL monitor s internal circuitry includes digital to analog convert ers DACs and amplifiers to map these digital sig nals onto the screen in the correct position and at the appropriate intensity While the term TTL based video may not be familiar you may have heard of MDA Monochrome Display Adapter CGA Color Graphics Adapter and EGA Extended Graphics Adapter cards These cards are all TTL based and they typically use DB 9 Connector Used for DB 9 9 pin D connector TTL Video Connection outputs Interestingly while the earliest PCs used digital video some of the most modern models are moving back to the digital realm only not using MDA CGA EGA standards You ll see this in high reso lution flat panel displays such as Liquid Crystal Displays and Plasma Displays as well as in some monitors that utilize Universal Serial Bus USB
6. in certain pc board disconnects etc The screw in D connectors on some KVM cable sets are con sidered to be positive locking as contrasted to typi cal PS 2 type DIN 6 connectors which can discon nected accidentally under strain pot To embed a component in a material within a casing that becomes part of the product primarily for protection though it may be to thwart the theft of circuit details Alternatively an abbreviation for potentiometer Potentiometer pot A popular term for a vari able resistor potting The sealing of a component e g the cable end of a multiple contact connector with a plastic compound or material to exclude moisture prevent short circuits provide strain relief etc Pot ted or molded cable ends are generally more dura ble than those which snap glue or screw together power brick A small power supply either a transformer or a transformer plus rectifier which plugs into an AC outlet and has a cable leading to the device it powers Power bricks are commonly used on modems and other smaller electronic devic es as well as on some KVM switches and extend ers They are used for a variety of reasons includ ing less costly to purchase an off the shelf supply than to design it into the equipment removes heat producing components from the main chassis removes noise and hum generating components from the vicinity of sensitive circuitry and provides a means to purchase an opt
7. A computer memory that interfaces directly with the central processor It is optimized for speed and has a limited capacity Its purpose is to supply the central processor with the data for the immediate computation without the delays that would be encountered by interfacing with the main memory Also known as cache mem Ory SDLC An IBM data communication protocol sector The smallest addressable unit of informa tion set of bits in a rotating computer memory such as hard disk floppy disk or CD DVD semiconductor Materials whose electrical con ductivity is between that for good conductors and that for good insulators Their conductivity may be changed by heat light electric field or magnetic field The intentional doping with specific impuri ties may also change them Examples include ger manium lead sulfide lead telluride selenium sili con and silicon carbide A semiconductor device such as a transistor is frequently referred to simply as a semiconductor semi rigid A cable containing a flexible inner core and a relatively inflexible sheathing sensitivity Measure of the ability of a device or circuit to react to a change in some input Sensitiv ity can also be the minimum or required level of an input necessary to obtain rated output as in an amplifier Page 72 serial operation The flow of information through a device in time sequence using only one digit word line or channe
8. An interconnected array of active and passive elements integrated with a single semiconductor substrate or deposited on the substrate by a continuous series of compatible pro cesses and capable of performing at least one com plete electronic circuit function Normally only the input output and supply terminations are acces sible Also called monolithic circuit and monolithic integrated circuit When transistors or other discrete components are separately mounted and connected itis a hybrid integrated circuit Intellimouse Microsoft s trademark for a spe cial type of computer pointing device originally developed by them for use with Windows applica tions It consists of a two button mouse with a small wheel between the two buttons The wheel is used for scrolling and pointing functions with compatible software applications Also known as a wheel mouse Because it uses different data encoding it requires different mouse drivers to function For this reason only certain late model KVM switches and extenders can be used with an Intellimouse Moreover not all KVM switches and allow use of computers whose operating systems probe for such a mouse interlaced Refers to a method of displaying a video image on a monitor or television screen An interlaced image consists of two sequentially scanned fields which together comprise one frame of video Thus if the video is displayed at 30 fps frames per second
9. In a 256 color display colors are defined by color tables and each entry has three six bit color fields Thus the scale of possible colors is 64x64x64 or 262 144 possible colors but only 256 at any one time These 256 col or subsets are sometimes called color palettes 16 777 216 32 768 A Y O Q o 2 Oa oa Ls 0 gt 23 Ec 2 gt V 16 4 Bit 8 Bit 16 Bit 24 Bit Color Depth Number of Bits to Represent Color The Number of Colors Displayed Depend on The Video Driver Card and The Software Not The Monitor A 16 7 million color display uses an 8 bit inten sity signal to define 256 levels of brightness for each of three colors red green blue mixing the three color s 256 x 256 x 256 levels of intensity produces 16 7 million colors so palettes are not necessary You will sometimes find 32 bit color software used for 8 bit representations of 4 color CMYK Cyan Magenta Yellow blacK ink on paper printing but the monitor is inherently a 3 color device where black is the absence of any color so it needs a maximum of 24 bits not 32 Sync While SYNC synchronization frequency is directly proportional to refresh rate it is not the same thing Typical vertical sync frequencies vary from 57 Hz Hertz or cycles per second to 100 Hz The frame rate or refresh rate equals the ver tical sync frequency in a non interlaced monitor which is what most computers use For an inter laced
10. it probably will NOT be compatible with a KVM switch even though you can usually plug it in As we outlined earlier Macintosh models that support external video do it either through video circuitry built into the motherboard or via plug in display cards Mac video is analog Those Macs which use motherboard based video differ in the maximum resolution and color depth and often both can be increased by plugging in additional video RAM Currently the maximum onboard video capa bility of Macs is as high as 16 7 million colors and as high as 1152 H x 870 V pixels though there may be a trade off of color depth for resolution due to video RAM limitations Plug in display cards are available with resolutions up to 1280 H x 1024 V pixels a few cards offer extremely high resolution of about 1664 H or even 1900 H pixels x 1280 V at color depths to 16 7 million The refresh rate of Mac monitors is not fixed either but it is gener ally about 72 or 75 Hz and occasionally up to 100 Hz on better video card monitor combinations The method of sync was also different from PC moni tors on early Macs Early Mac video color cards superimposed the sync pulse on the green video signal To further complicate matters most Power PC Mac models are capable of connection to VGA monitors either directly or with the addition of an inexpensive approximately 15 in line adapter In order to mix traditional Mac video with PC video in a given KVMS and to dri
11. later IBM developed the PS 2 protocol to differ entiate a new generation of computers Not sur prisingly the PS 2 command set relied upon ele ments of these predecessors Almost immediately IBM opened PS 2 protocol for use by other manu facturers but they also ceased development efforts PS 2 AT and AT PS 2 Type Keyboard Adapters on the PS 2 command set While the current PS 2 command set has been expanded by a variety of manufacturers on their own initiative PS 2 is real ly is not a well defined specification Nonetheless a keyboard video switch that is built to accommodate any PC must be able to handle gracefully historic as well as non standard ill defined variations in keyboard coding For this reason you will find some switch models do a better job with certain PCs or keyboards than do others Sometimes a firmware update in the switch will be required to accom modate some new model of PC and other switches cannot be updated Macintosh computers except the very earliest models which had RJ style phone connec tions used a separate bus for keyboard signals the ADB Apple Desktop Bus connector is a 4 pin mini DIN It carries not only keyboard but also mouse or trackball sig nals Other accessories can be attached to the ADB as well including modems graphic tablets and software copy protection keys or dongles As mentioned in the introduction recent Macintosh Models iMac G3 Yosemite G
12. there are 60 fields per second The visual impression of a single field is left by a combination of screen phosphor persis tence and the psycho visual blending that occurs within the viewer Interlaced displays are not as sharp for display of precise text and graphics and are seldom used in computer applications though they are the standard for conventional television I O input output Pertaining to the equipment used to communicate with a computer and the data involved Ina KVM switch this may also refer to the keyboard video and mouse ports that transfer data to from the computer or switch system Page 63 J jack A connecting device into which a plug can be inserted to make circuit connections jacket A rubber or synthetic covering applied over the primary insulation braids shields cable components or over the cable itself JAN specification Joint Army Navy specification K keying A mechanical arrangement of guide pins guide sockets keying plugs contacts bosses slots keyways inserts or grooves in a housing shell or insert that allows connectors of the same size and type to be lined up side by side with no danger of making a wrong connection Keying may also be accomplished by numbering the connectors and matching panel positions or by using connectors of a different size or color Under certain circum stances keying and polarization may be combined in a connector design keyway A slot or
13. Braided Shield Foil Shield The Appropriate Type of Shielding for The Application is One of Many Factors Affecting Cable Quality Monaural Microphone and Stereo Speaker Mini Phone Plugs on a KVMS Cable Set sideration Some models favor daisy chain only or star only topologies which limits installation flex ibility Other models permit a mix of topologies Some models require special interconnect cables and in more and more cases ordinary Cat 5 cabling has become the preferred method because it is read ily available relatively inexpensive and uses less space per connection The maximum distance from chassis to chassis and across the entire system from CPU to user console also differs with various makes and models Review these factors as they apply to your situa tion before making a purchase decision KVMS Reliability and Support Costs There is no question about it when you use a KVMS you are creating potential point where a failure can affect your access to multiple computers Thus KVMS reliability is a crucial concern The KVMS should be manufactured by a vendor with a proven track record using top quality components and extensive quality controls Its design should be conservative and should be such that a switch failure in one channel does not cause computers on other channels to be affected nor does it damage the computer Ideally there should be a way to patch around or otherwise hot wire the system f
14. It usually consists of a housing with contacts or a shell with modules or inserts and contacts and the necessary hardware to hold the assembly together and or make the assem bly a functional connector Page 56 console A set of computer peripherals used for I O control Typically includes a minimum set of a keyboard a video monitor and often a mouse A broader definition includes audio speakers and or microphone and other serial or RS 232 device The console for many Unix based computers and hard ware devices such as routers is terminal that uses ASCII communication code via RS 232 or similar serial interface and does not use a mouse May also refer to a piece of furniture from which one or more computers or video monitors are viewed and controlled console access ratio A mathematical expression of the number of consoles connected keyboard monitor and mouse to the number of available computers in a given KVM switch system Also see user access ratio contact An electrically conductive item designed for use in a multi circuit connector for convenience in making multiple electrical connections contact resistance Measurement of electrical resistance of mated contacts when assembled in a connector under typical service use Electrical resis tance is determined by measuring from the rear of the contact area of one contact to the rear of the contact area of its mate excluding both crimps while carrying a spe
15. T e E E TEN 46 e KVMS Reliability and Support Costs 2 0 0 eens 47 e Efficiency and Productivity Less Tangible But Very Significant Sources of Savings 47 Appendices e A Connector diagrams pin outs fUNCtiONS ccc 49 e B KVMS Glossary cc 51 Who Created This Document c c ccc 78 Page 1 What is KVM Switching A Keyboard Video Mouse Switch KVMS is also known as a Keyboard Video Switch KVS same thing These devices allow multiple computers to share sequentially one keyboard monitor and mouse In recent years more advanced multi con sole switches have become popular They support multiple data paths so that two or more monitors keyboards and mice can address any of the con nected computers same concept greater flexibil ity While the concept itself is simple KVMS tech nology has evolved only recently It was introduced in rudimentary form during the late 1980s and has matured during the 1990s Why was KVMS technology developed Why it has been growing so rapidly in popularity Isn t it really pretty easy to build such a switch As you read this document you ll find the answers to these questions and some others you ve probably not yet considered NOTE Originally published in black and white print this Second Edition is offered primarily as an Adobe PDF file Portable Document Format so that we can use full color illust
16. a full range of platform support in many cases this will not be a deciding issue Administrators who do have a mix of platforms should be alert to the subtleties of platform support available form a given switch For example can the Sun keyboard with its special ized function keys be used at the console or must the Sun platforms controlled via KVMS translation from PC keyboards Multi console KVM Switches without native support can obtain video sync conversion or key board and mouse protocol translation through the use of adapters One important aspect of Native vs Adaptive platform support is the cost In an environ ment where a high number of computers represent a mix of platforms the cost of installing protocol converters can be extremely expensive If you select a KVM Switch based on its price alone and fail to consider the cost of external converters and or spe cial adapter cables the overall cost may end being much higher than a product you initially dismissed due to sticker price Controlling and Tracking Usage in the KVM Switch System The traditional approach to KVM switching has been based on an external hardware based solu tion Users did not want any software or firmware added to their servers so the switch manufacturers created hardware that did the job entirely external to the servers However the latest trend and product releases are includes external software and or hard ware as a control mechanism or enhanc
17. amp amp 7 8 9 16 CPU to KVM CPU to KVM CPU to KVM CPU to KVM Switch or Ext Tx Switch or Ext Tx Switch or Ext Tx Switch or Ext Tx System System System System Chassis Chassis Chassis Chassis User Interface Chassis are equally connected to the KVM Hub Hybrid Three Hybrid Topology models are displayed to illustrate a minimum of set of topology options or alternatives In these Hybrid models any tier is capable of establishing a continued connection to another tier as either a Star or Series model Displayed in Hybrid Figure A is a first tier chassis connected to the second tier and then to a third tier System Chassis and or KVM Hubs Multi Console Keyboard Video Mouse User Router Chassis Chassis Multi Console Keyboard Video Mouse Multi Console User Chassis Keyboard Video Mouse 1 Router Chassis Multi Console Keyboard Video Mouse Multi Console Router Chassis Keyboard Video Mouse User Chassis Multi Console Keyboard Video Mouse Router Chassis Multi Console Keyboard Video Mouse User Chassis Multi Console Keyboard Video Mouse Router Chassis Multi Console Keyboard Video Mouse Router Chassis Multi Console Keyboard Video Mouse User Chassis Multi Console Keyboard Video Mouse Router Chassis Multi Console Keyboard Video Mouse Router Chassis ee 2 Page 37 via a Star model The chassis connections between tiers three and four in Figure A follow the Series model Hy
18. are widely used in internet related applications due to the excellent multi tasking capabilities and security features of this O S USB Acronym for universal serial bus A set of serial port standards and connectors promulgated in the late 1990s for medium speed data communica tions in small computer systems USB connections are used for keyboards mice graphics tablets scan ners modems printers digital still cameras and some slower mass storage media They are not suit able for high speed video hard disk access and so forth USB was meant to replace PS2 I O connec tions as well as a limited variety of traditional serial port parallel port and SCSI port connections user access ratio A mathematical expression of the number of users people actively using a key board monitor and mouse to the number of avail able computers in a given KVM switch system This is not necessarily the same as console access ratio since there can be more console connections than are actually used at once UV Abbreviation for Ultraviolet V voltage Symbol E The term most often used to designate electric pressure that exists between two points and is capable of producing a flow of current when a closed circuit is connected between the two points Voltage is measured in volts mil livolts microvolts and kilovolts The terms elec tromotive force potential potential difference and voltage drop are all often called voltage vol
19. can be exchanged to upgrade the firmware electromotive force EMF See voltage electrostatic discharge The sudden discharge of electrostatic charge that occurs when a charged con ductor is grounded EMI Electromagnetic interference Unwanted electrical or electromagnetic energy that causes undesirable responses degraded performance or complete malfunctions in electronic equipment emulator An electronic circuit or computer pro gram that performs functionally like another circuit or program for example a computer of one manu facturer emulating that of another manufacturer or a KVM switch emulating presence of a keyboard and mouse to a connected computer encoder A device which translates information from one form code to another e g decimal to binary encoder Normally an encoder is used in the device sending the information An encoder can be created on a general purpose computer using appropriate software as contrasted to using a dedi cated electronic device or chip for encoding EPROM Erasable programmable read only mem ory A ROM in which the programmed data can be erased and the chip reprogrammed it differs from the RAM in that the erasing and reprogramming requires special equipment not part of the system in which the EPROM is used Extender In the context of computers this is a device which allow the keyboard video monitor and mouse and sometimes other peripherals to be located at a gr
20. ciated with annual maintenance of keyboards and monitors A 50 reduction of floor space is typical when using KVMS and you can get down to 25 the floor space if you combine specialized racking sys tems with KVMS If you are installing new systems often the cost of the KVMS will be offset completely by the money saved on monitors keyboards and mice if you use them For example a decent quality 17 inch VGA monitor sells for about 350 and a 101 key keyboard with a mouse goes for 35 to 60 Let s suppose you eliminate seven such moni tors and keyboards with a single 8 1 KVMS The switch and cables can cost under 1 200 The moni tors and keyboard savings are about 2 800 an immediate savings of about 1 600 If those were high resolution pricey graphics monitors you elimi nated your savings would be far greater Your savings may be reduced slightly if the keyboards come with the computers but you still have the ongoing power and maintenance savings we have previously described so the basic keyboard video mouse switch not only pays for itself right away it pays you back big dividends year after year Page 5 Benefits to Software and Hardware Developers The developer must test his software or circuitry on a variety of computers For this reason the typi cal developer s office is itself a mini lab equipped with two to four workstations A 10 x 10 foot or 12 x 12 foot cubicle can become very crowded wher
21. clamp A device used to give mechanical support or strain relief to a wire bundle or cable CAD An acronym for Computer aided design Use of the computer in engineering design activities CAM Computer aided manufacture Use of com puter to aid and direct manufacturing activities capacitance The property of an electrical non conductor dielectric in a capacitor that permits the storage of energy as a result of electric displacement The unit of capacitance is the Fara day though typical capacitor values are usually expressed in microFards or picoFarads millionths or billionths of Farads capacitive coupling The coupling of energy from one conductor to another as a result of the dis tributed capacitance between them With resistance one component of capacitive reactance capacitor A device to store electricity and release it when needed this consists of conducting plates or foils separated by thin layers of dielectric The plates on opposite sides of dielectric layers are oppositely charged by a source of voltage and the electrical energy of the charged system being stored in the polarized dielectric Capacitors block the flow of direct current dc while allowing the flow of alternating current dc and are therefore used as elements in filter circuits carrier A higher frequency upon which voice or coded data can be superimposed modulated cascade To take the output of one amplifier and apply it as t
22. con nector for many years though it has gradually been superceded by the smaller PS2 style connector and by USB connectors The data format for signals in these various connections is also different asynchronous transmission Transmission in which time intervals between transmitted bits may be of unequal length The transmission is controlled by start and stop bits which frame each character or string of data attenuation A reduction in power which occurs during signal transmission through cables broadcast or other means May be produced intentionally by placing an attenuator in a circuit Attenuation 1s generally expressed in decibels or decibels per unit of length distance AWG An acronym for American Wire Gauge Page 52 B backbone The part of a computer network that carries the heaviest traffic It is the main trunk cable from which all connections to the network are made It may be comprised of copper cable or fiberoptic backplane Area of a computer or other equipment where various logic and control elements are inter connected balanced line A two conductor line in which both conductors have the same impedance with respect to ground Since noise pickup is equal on both conductors common mode interference is cancelled at the load bandwidth Defines a range of frequencies that can be accommodated For example for a bandpass filter it is the frequencies passed For a transmitter and receiver it is
23. cost more but impose less signal degradation If the capacitance between conductors is incorrect the cable becomes a low pass filter reducing bandwidth and impairing video quality Adequate shielding is important to reduce interaction and interference cables differ drastically in this regard For example they may have swerved wire wrapped braided or foil shield these methods of shield ing trade flexibil ity against shield effectiveness and durability Coaxial cable can be bene ficial here though it is typically more costly and less flexible than other cables Earlier KVM extension and interconnect tech nologies occasionally used Category 5 cabling to convey keyboard mouse and video over longer dis tances Then it was typical to use two Cat 5 cables per pathway Today advances in KVM encoding have made it possible to pass these signals over a single Cat 5 cable and to include serial data as well as stereo microphone and speaker signals as well Cost reduction and miniaturization even make this practical to convey connections from individual CPUs to the KVMS switch thus simplifying the cabling and further sav ing precious rack space On the other side of the switch existing Cat 5 cables can now be used to run the keyboard monitor mouse control console out to the user s office Connection between the switch chassis on larger multi chassis sys tems is an important con Wrapped or Swerved Shield
24. extend ed the protocol to support a third button and a few other manufacturers created their own protocol exten sions On the Microsoft serial mouse the protocol utilizes 3 bytes whereas Logitech s serial mice use 5 bytes the additional bytes being active only when the middle mouse button is activated These differ ences help explain why many mice are sold with proprietary software drivers they contain the exten sions for special functions that are not included in the computers basic software Of course KVM switch manufacturers have to be able to deal with this wide variety of extensions without the benefit of being able to load up the drivers because switches have traditionally been built to work externally to and independently of the connected computers Clearly a KVM switch designed only for a pure 2 button mouse wouldn t behave well with a Logitech 3 but ton mouse in fact they usually lock up or work intermittently Eventually most KVM manufacturers figured out how to deal with more popular non standard mice but this example illustrates why so called standards aren t sufficient to ensure that a KVM will simply work no matter where it is used Serial Mouse communi cation is one way from mouse to computer This point is significant as you will soon learn The PS 2 mouse is so named because it was developed by IBM with the introduction of their DB 9 Female Connector on a Serial Mouse KVM Cable PS 2 Key
25. flat packages which have leads on the two longer sides The package material may be plastic or ceramic DIPs can be integrated circuits packages of resistors and other circuit elements On some KVM switches and extenders DIP mounted miniature switches DIP switches are used to set interface characteristics logical address es and so forth duplex full Method of operation of a communica tion circuit whereby each end can simultaneously transmit and receive information duplex half Permits one direction electrical com munications between stations Half duplex may per mit operation in either direction but not simultane ously Therefore this term is qualified by one of the following suffixes S O for send only R O for receive only or S R for send or receive E E Symbol used for voltage Also written e EAROM Acronym for Electrically Alterable Read Only Memory A reprogrammable ROM in which each cell can be individually erased by a special electrical process EBCDIC Extended Binary Coded Decimal Inter change Code An 8 bit code used to represent 256 unique letters numbers and special characters edge connector A connector into which the edge of a printed circuit board is inserted EEPROM Acronym for Electrically Erasable Pro grammable Read Only Memory A reprogrammable ROM that can be reprogrammed by means of spe cially applied signals EEPROMs are often used to store firmware in KVM switches and
26. from a coded form into a more usable form e g binary to decimal decoder Normally the unit receiving the data uses a decoder degradation A deterioration in performance or quality usually attributed to a specific cause or causes For example the differential capacitive reactance in the conductor pairs used to convey red green and blue signals will cause a degradation in video quality as cable length increases demodulator A device used to extract data or sig nals when a carrier wave is employed as the means of data transmission To obtain the data transmitted the demodulator must receive and filter out the car rier wave from the signal with which it was origi nally modulated See decoder derate To reduce the rating of a device for improved reliability or to permit operation at high ambient temperatures dial up An expression to describe the ability to initiate a station to station telephone call and effect the station connection desired purely as a result of dialing Commonly referred to as a telephone modem based connection Page 58 dielectric A material that serves as an insulator 1 e it has poor electrical conductivity A measure of resistance to voltage exhibited by a given insula tion dielectric withstanding voltage Maximum poten tial gradient that a dielectric material can withstand without failure Value obtained for the dielectric strength will depend on the thickness of the mate rial an
27. ge lt Ka 4 3 1 SGI Personal IRIS 4D 20 amp 4D 25 Keyboard amp Mouse oo L a L ov DB 9 Keyboard Cable Female in Chassis SGI Indigo Crimson and other SGI 15 Pin Keyboard amp Mouse DB 15 Keyboard Cable Ph ss O XD 2 aS PP os OX 8 7 6 5 4 3 gt L P E 14 13 12 PU 9 xx CWC or L ahh G 9 1 2 3 4 5 O N O O V Serial Mouse DB 9 Male in Chassis Connector Pin Configurations for Keyboard Mouse and USB ADB and USB also handle other data besides Kbd amp Mse Page 50 Pin Arrangements are Shown from Mating Side of Connectors Not to Scale Red Grn Blu ID2 Gnd RSS CS RED XN G O GRN BLU VGA Video A1 12345 A2 A3 HDD 15 SUN amp SGI Video Female in Chassis EE gt T O 13W3 Female in Chassis ERAT Rgn Sgnd Middle SANYO WO Ggnd Key Row OZ 9 Red Grn Blu Res Gnd SS L S N VESA Video SRP O ROR j HDD 15 1 2 3 4 5 6 7 8 Macintosh Video Female in Chassis Early non VGA DB 15 j TREE TURE E TRE DECREED Female in Chassis g g Rgnd Middle 5vdc Ggnd Row a LL GyO sSs TTL Video The Early Digital Signal in 3 Types DB 9 Connectors Female in Chassis O NY D X KOs lt xX Soy AE We WO PHO SIR L OI 5 4 3 2 1 Monochrome CGA amp Hercules c XQ ay yw WS of S gO x 9 8 7 6 o O gh 9 8 7 8 O oo 5 4 3 l NEO S SS REO 9 8 7 6 O 9S V N N Connector Pin Configurations for Various Video Connections Commonly Used in KVM Swi
28. groove in which a key engages kilo Metric prefix meaning 1 000 KVM Acronym for Keyboard Video monitor Mouse May refer to a switch or to the actual peripheral devices for a computer See KVMS KVM Extension See Extender KVMS Acronym for Keyboard Video monitor Mouse Switch A device which enables one or more consoles typically consisting of a video monitor a computer keyboard and a mouse or simi lar pointer to control two or more attached comput ers kWh Kilowatt Hour A measure of power usage 1 kWh is 1000 watts dissipated for one hour L LAN An acronym see local area network LCD An acronym for liquid crystal display A multi element display device consisting of a liq uid crystals hermetically sealed between two glass plates Originally the LCD readout was either dark characters on a dull white background or white on a dull black background The white could take on a blue or green color if various types of backlight ing or tinting were used Later color LCD displays were developed and current multi layer LCD tech nology permits 24 bit 16 million color representa tion leading edge The leading edge of a pulse is defined as that edge or transition which occurs first The leading edge of a square wave signal is usually the transition from a logic 0 to a logic 1 LED An acronym for light emitting diode light emitting diode A semiconductor diode gen erally made from gallium a
29. more common with GUIs use more power so you d save more Like they say in the automotive EPA mileage analyses your results may vary Adding the HVAC and direct power savings and averaging the power rate to 12 5 cents KwH the power savings alone of an 8 1 keyboard video switch in one year will be about 2 300 To this add the savings in floor space and you can see the switching will just about pay for itself in the first year of operation There are actually much greater savings for your company if you consider capital acquisition and maintenance for the key boards and monitors and a measurable increase in operator productivity LAN Administrators Can Save Time Simplify Management and Fit More in Available Space When a monitor and keyboard is attached to every CPU in the data center the operator typically must walk up and down long aisles of computers to review the operating status of each server bridge router etc If we instead use a Keyboard Video Mouse Switching system to create a one or two seat console for dozens of servers we make the manager s task much easier If you re the operator you will really appreciate how much more relaxed you feel at the end of the day Page 4 pect POWER p lowatt poWER SAVINGS Lace ae 365 08 DIRECT E jonat Hours D pay in a lt Power Por 365 D8 gt Mo sage 24 Year R S in Watts Day S S X lt oS 3 F 2 m 2 lt 2 oS D gt
30. of solid state devices rather than magnetic tape memory RAM has read and write capabilities Some optical devices CD RW and DVD RW are used as a type of RAM though this is not generally what is meant when referring to RAM memory volatile A computer storage medium which is incapable of retaining information without continuous power dissipation metric prefixes A series of prefixes used in the metric system to modify a unit of measure The most commonly used in electronics are as follows giga G 10 mega M 106 kilo k 109 centi c 1072 milli m 10 micro m 10 6 nano n 10 pico p 10 12 mho Unit of conductance Reciprocal of an ohm One ampere of current passing through a material under a potential difference of one volt provides one mho of conductance Also called siemens microprocessor A single chip or small group of chips that contain all the functions of a central processing unit does not include peripherals microwave That portion of the electromagnetic spectrum lying between the far infrared and con ventional radio frequency portion Frequency range extending from 1 GHz to 300 GHz Microwaves are usually used in point to point communications because they are easily concentrated into a beam and thus do not waste energy by radiating it in unwanted directions milli A prefix meaning 103 or one thousandth One millivolt would be 0 001 volt modal dispersion The spreading of a light sign
31. per frame with half the image information To connect a computer to a TV circuitry is needed to convert the video to interlaced images at the correct vertical sync frequency Typically a loss of resolu tion and a degree of jitter or aliasing occurs with this conversion image degradation is particularly noticeable when displaying text or line drawings With the exception of a few TV sets that have monitor capability defined as separate R G B or red green blue and sync inputs the TV is meant Page 31 to receive an ultra high frequency phase modulated broadcast signal that contains the video and audio information Thus in order to connect a computer to a TV set as opposed to a TV monitor a modulator is also required The modulator typically converts RGB video to TV channel 3 or 4 frequency signals that are subsequently treated by the TV receiver just like a normal broadcast station s signal Full size full motion NTSC broadcast Television images require 4 MHz to 6 MHz of bandwidth MHz is a Mega Hertz or one million cycles per second A 90 MHz Pentium equipped computer will require almost all its processor power to handle full motion broadcast video with audio and video production or effects work on a computer demands a much more capable processor TV sets don t have to have such processing power because they typically handle the signal in the analog domain not as a digitized data stream However broadcast video dem
32. requires a suitable micro processor or intelligence in the switch Similar considerations apply to mouse operation serial vs PS 2 vs wheel mouse if the KVM switch is to be widely compatible Switches that gracefully handle all these emulation modes without errors are said to have Robust Emulation capabilities The purpose of emulation simply stated is to make the computer think it is connected to its normal keyboard and mouse even though it is actually connected to the KVM switch For more information on emulation see Emulation Services Video is more complex Some switches merely pass the video straight through routing the signal from the selected CPU to the connected monitor However better switches correctly terminate the video output of non selected computers to keep the computers video cards suitably loaded and to avoid spurious signal emissions that might other wise cause interference fuzzy ghost images on screen A few models allow the user to compensate for color shift or brightness contrast changes due to cabling or differences in video driver cards Switches that accommodate XGA II Sun SGI or Macintosh computers have circuitry that returns appropriate information to the computers indicating the size resolution and color depth of the connected monitor Certain highly capable KVMS models also include circuitry to convert between video formats 1 e Mac or SGI with Sync on Green to VGA with Compo
33. set in the VT 100 terminal series Subsequent code sets include more escape codes and are designated for use with terminal standards such as VT 220 VG 320 and so forth though all use RS 232 serial protocol Page 13 How Does A Keyboard Video Switch Work Passive Versus Active Switches The earliest and least complex switches were passive That is they had no powered electrical components in them You would turn a rotary switch or engage one of several interlocked push button switches to connect the attached monitor and sometimes a keyboard to the desired com puter This type of switch is still sold occasionally and a few have been enhanced to also switch mice The mechanical switch s chief advantage is low ini tial cost but it has a number of offsetting disadvan tages including spiking of video transients that can blow sensitive circuits loss of mouse or keyboard sync and no emulation so that each computer must be booted in sequence instead of simultaneously after a maintenance shut down Active KVM switches have powered circuitry that handles the video keyboard and in modern designs the mice Depending on the switch design you either push up down buttons to step through connected CPUs you press direct select pushbuttons or you place the switch in an auto scan mode that cycles through the connected CPUs at some preset interval Many models permit direct selection of the desired CPU by means of keyboard com
34. software is added to the servers so security is much less apt to compromised and the computer cannot be impaired by any software incompatibility In addition if a server must be rebooted the remote client requesting the reboot can observe and control that process right back to blue screen or CMOS setup something not pos sible with a pure software solution Moreover only one network or modem connection is required to access any number of servers Page 45 Page 46 Dollar Factors Obvious and Hidden You can compare the price tag on a given switch including its required cables and accessories to another and get some feel for the relative costs of this KVMS versus that one And you can compare the cost of the KVMS with a single monitor and keyboard to that of one monitor and keyboard and mouse if applicable per computer Such an analy sis however will not really give you a clear picture of the true cost of implementing KVMS KVMS Direct Costs Active keyboard video switches for a particular type of platform are priced over a wide range Some platforms are more costly to switch with wider bandwidth or special connectors or instance some can support longer cables some have more sophis ticated technology and some are just plain better values Some switches offer extraordinary capabili ties such as multi platform compatibility extreme distances beyond the typical 5 to 30 feet between computer and switch or
35. that goes into a receptacle measuring about 8 mm x 16 mm exter nally 0 31 x 63 The nearly square B standard is for use with devices that have detachable cables the B plug measures 8 0 mm wide x 7 26 mm high 31 x 29 and goes into a receptacle measuring about 11 5 mm x 10 5 mm externally 45 x 41 B connections are only made on a chassis not for in line extension Both the A and B standard USB connections utilize four internal conductors plus a shielded jacket Without going into detail about the USB proto col for mouse or keyboard at this time it does represent the first time that a true well defined platform independent standard is being promulgated and adopted throughout the computer industry At the time of this writing a few small KVM switches have USB capability but none of the larg er However off the shelf USB to PS 2 and USB to ADB adapters are available for 50 to 100 each and they allow USB type devices to be inte grated into traditional KVM switches Eventually we expect to see larger USB capable KVM switches that do away with the need for adapters However the implementation is not as simple as it would seem due to the way USB works and the way USB databases are built by each USB equipped computer or hub lt USB 1 1 spec gt USB B Type Connector USB A Type Connector What it Takes to Deliver a Good KVM Switch Today almost any company can put a KVM switch on the market
36. 0 ohms A resistor also has a power handling rating measured in watts which indicates the amount of power which can safely be dissipated as heat by the resistor resonance The frequency at which capacitive reactance and inductive reactance are equal and therefore cancel one another s effects RETMA Abbreviation for Radio Electronics Television Manufacturers Association Now changed to Electronics Industries Association EIA rf Abbreviation for radio frequency RGB Abbreviation for Red Green Blue the pri mary phosphor colors in most color video and tele vision monitors Also refers to a means of repre senting the color spectrum within computer pro grams and files Used for radiated or transmissive color not for reflective color representation RG U RG U is used to designate coaxial cables that are made to a Government specification In the case of RG58 U the R means RADIO FRE QUENCY the G means GOVERNMENT the 58 is the number assigned to Government approval and the U means it s a UNIVERSAL specifica tion Some video signals are better conveyed over longer distances by coaxial cables and these are specified by RG U values ribbon cable Round conductor flat cable A form of flexible flat cable consisting of parallel round conductors in a flexible insulating material and designed for mass termination ring network A network topology in which nodes are connected as point to p
37. 4 G3 Powerbooks are shipped with USB connectors and include USB keyboards and mice Fortunately except for the G4 they also have ADB connections for keyboards mice so they work with conventional Mac or multi plat form KVMS ports For the G4 use a USB capable KVM switch or a USB to ADB or USB to PS2 adaptor A handful of platforms and keyboards have keyboard control anomalies AST s keyboards used IBM s scan codes but introduced variations in sig nal timing and drive capability which made physi cal interface tricky Compaq pioneered autosensing XT AT keyboard technology When IBM introduced their 101 key keyboard with autosensing they did it differently from Compaq Compaq has not fully implemented the IBM autosensing protocol but has adopted multiple scan sets Thus effective switch emulation of IBM s and Compaq s various key boards can be particularly daunting At one time NCR and Leading Edge used the Keyboard Reset signal defined only on the old 5 pin DIN connector Original Macintosh ADB Apple Desktop Bus Connector Used for Keyboard and Mouse as well as certain other data Page 19 which had to be passed through to the CPU for suc cessful booting these were XT and early AT com puters now mainly obsolete Macintosh keyboards use different scan codes and they are l way The Mac CPU will boot with or without a keyboard so keyboard emulation is not needed on the Macintosh though USB models ma
38. Icx Mac IlIci and most of their 68040 Quadra and BNC Connectors Used for ka erforma and Some Mac SGI RS 6000 Me Majority of Power and Special PC Video Cards PC platforms the latter sometimes using plug in video cards The color depth varies from mono chrome to 16 7 million colors and screen resolution varies as well For this reason and because the Mac operating system relies on a GUI graphical user interface all but the earliest Mac models return information from the monitor or video card to the operating system Video sense data indicates the resolution and color depth of the monitor being used so the operating system can render its windows appropriately These complexities are a key reason why a Mac KVMS was not introduced until several years after PC switching became available Until very recently the Macintosh s keyboard and mouse signals were also defined by a different electronic standard the ADB or Apple Desktop Bus which is why an ordinary switch cannot be used to handle Macs and PCs together Finally the very latest Macintosh models including the iMac and the new G3 Yosemite models as well as the latest Powerbooks include USB universal serial bus connections that can be used for mouse keyboard and even video connec tions as well as modem 1 o and other functions Most of these models have redundant Mac standard ADB keyboard mouse and both DB 15 Mac and HDD 15 VGA video connecto
39. OSE AS op eases was EESK see e EZES get ees 2898385722828502 ope SMES SES eS SR Se ECHL HBS Fe PSP shes Zeno FZ E 3 hn 8 5 3 5 5 7 S 7 E lt 8 2 O 9 75 5 S 9 Z 3 SRDA Redo L o gyel 2 883 2 575405583358 8882 BERSLES ESE Z PLS SES ERE Sey sO Du o HB hy gt gE e lt SREP HOS 2 TSHEOuyLsdons j Oq5836828 RS Se 8288228 g a JP O V S O BABE ESSERE SRES es RSE Gy Sg oes eres esas t A Pe o q 3 oad 2 lt lt 8 acd gt S ovac egas 2 Z nx s amp 25 n 88 z 3 S rt Z D O 5 n f S LU AED B Pe Oo AUS 9083255547 882805 Sasa 0 U s EUS S 3 56 Sao Soper ES ae ec Aa mmm o0o o7758083 E D 3 Os 2 5 950 8o dE SSY Da 0080 20 0 053 Sopa OFMTVOR EFS RSYeEDAVSEAESCEHD V o SR78868 83000228 88 O E n Q e A D S Padeda CS O Eg EHESEESES SERS SSS SESS SHSSCUPGERSSSCSOHSERE SEL Page 28 or about 100 mV per Third party vendors pushed VGA to higher limits with SVGA modes of have 256 steps of approximately 3 mV per step per 800 H x 600 V pixels or 1024 H x 768 V pixels step The super fidelity cards of 16 7 million colors each of three phosphor colors based on a 24 bit color field 8 bits per color mode is 8 3 bits per color neither CGA but they were adequate for text and primitive graphic display s standards 9 9 The EGA Extended Graphics Adapter card By today increased the color depth and resolution You could have 16 colors d
40. T The Trackpad is a technically different means of controlling a cursor but functionally it does the same job as a mouse or trackball It s a flat touch sensitive pad that may be built into a keyboard or a notebook computer or it can be in an external hous ing Trackpads are available in Mac and PC plat forms and they may require different driver soft ware in a given computer Not all KVMS systems are compatible with trackpads as input devices it depends on the particular trackpad or keyboard USB Standard PS2 amp Microsoft Intellimouse trackpad code and on the connections The Wheel Mouse which Microsoft developed and dubbed the IntellimouseTM looks like a con ventional two button PC mouse but it has a small control wheel between the two mouse buttons This wheel directly scrolls windows and performs other functions in savvy Windows software While a wheel mouse uses a PS 2 connector it requires a special software driver and is not auto matically compatible with all software it is defi nitely not compatible with all KVMS systems The Intellimouse has subsequently been introduced for the Macintosh product line with a suitable connec tor and different driver software the applications must support wheel mouse input or the unit has no effect If your computer has wheel mouse drivers or if you want to use a wheel mouse to control one or more KVMS controlled computers be sure the KVMS is compatible with
41. The context defines the technologies for example it may describe a mix of integrated circuit and discrete transistor circuitry hybrid IC A composite of either monolithic inte grated circuits or discrete semiconductor device circuits in a unit packaging configuration Hz abbreviation See Hertz I I Symbol used to designate current IC abbreviation See integrated circuit IEC International Electrotechnical Commission IEEE Institute of Electrical and Electronics Engi neers IEEE 488 An interface standard for interconnect ing programmable digital instruments impedance Z The total opposition offered by a component or circuit to the flow of alternating or varying current Impedance is expressed in ohms and is similar to the actual resistance in a direct cur rent circuit In computations impedance is handled as a complex ratio of voltage to current impedance match The condition in which the impedance of a component or circuit is equal to the internal impedance of the source or the surge impedance of a transmission line thereby giving maximum transfer of energy from source to load minimum reflection and minimum distortion Imperial Wire Gauge See British Standard Wire Gauge Page 62 in band A reference in the context of this doc ument to the remote control of a computer by means of its LAN connection or a modem connec tion Such software packages as PC Anywhere LapLink a
42. VM extension or switching products you can perma nently damage the equipment be sure to use the proper type of Cat 5 cable In network applications standard Cat 5 cable is specified under ideal condi tions for data rates bandwidth to 150 MHz and distances to 100 meters 328 feet Enhanced Cat 5 cables may carry higher bandwidth signals and or extend the distance for data transmission However the same Cat 5 cable when used for KVM extension may not give equal results in terms of distance or bandwidth because the KVM signals are different than those used in Ethernet TCP IP data transfer environments The purely digital square waves of a TCP IP clocked transmission differ from the sepa rate Red Green Blue analog video traveling down different pair of Cat 5 conductors and differences in the phase timing of these signals due to dif ferent twist rates in each pair of wires within the Cat 5 cable will cause R G B spread or ghosting shadowing on the monitor Perhaps surprisingly some enhanced Cat 5 may perform worse than ordi nary Cat 5 in certain KVM extension applications Unlike the 100 meter 328 foot standard for data transfer the same copper wire Cat 5 cables can deliver satisfactory results for KVM transmission with cable lengths up to 500 800 or even 1000 feet depending on how the manufacturer s circuitry compensates for losses and time delay and depend ing on the maximum video resolution one wishes to conv
43. Windows and OS 2 typically run on Intel based CPUs and clones of those CPUs This includes the Intel 286 through 586 or Pentium series chips lower end Celeron chips AMD s K series or advanced Athalon chips Some KVMSs have had difficulties with the first Pentiums but then again so did Intel itself at one point The x 86 series chip is based on CISC archi tecture Complex Instruction Set Chip RISC Reduced Instruction Set Chip architecture is favored for running the Unix O S and variants of Unix Thus if a Unix based computer has compat ibility problems with a particular KVMS it may be the O S or the computer architecture causing the conflict and you should consult the KVMS manufacturer to resolve the issue Unix and Unix variants can run on Motorola 680xx series chips Several computer manufacturers used these CPUs for Unix or other O S s including the original Macintosh O S Macintosh products migrated from the 680xx family of CISC chips to the Power PC RISC CPU family several years ago the Power PC architecture was a joint develop ment effort of IBM Apple and Motorola IBM also markets Power PC based computers including a number of RS 6000 models The Power PC can be overlaid with various operating systems including Macintosh O S 7 through X Windows 95 98 NT OS 2 and Unix In summary it is essential that you verify that a given KVMS will work not only with the operating system s you plan to use but
44. a one way path for telegraph type signals Sine wave A wave which can be expressed as the sine of a linear function of time space or both A waveform often viewed on an oscilloscope of a pure alternating current or voltage single mode A fiber optic fiber that allows only one path for the light to take due to the fiber s very small diameter less than 10 microns Page 73 single pole A contact arrangement wherein all contacts in one position or another connect to one common contact skin effect The tendency of alternating currents to flow near the surface of a conductor thus being restricted to a small part of the total cross sectional area This effect increases the resistance and becomes more marked as the frequency rises sleeve The insulated or metallic covering over the barrel of the terminal small scale integration Abbreviated SSI A sin gle circuit function implemented in monolithic sili con In complexity a circuit of less than 10 gates SMD See surface mount device SNR See signal to noise ratio solder An alloy that can be melted at a fairly low temperature for use in joining metals having much higher melting points An alloy of tin and lead in approximately equal proportions is the solder most often used for making permanent joints in circuits Electronic components are soldered with rosin as a flux plumbing solder with acid flux will quickly destroy electronic circuits due to ox
45. active devices was because keyboard and mouse emulation was highly desir able and no satisfactory solution could be achieved with passive circuitry Intel based PCs running DOS or Windows the main platforms and OSs being switched at the inception of these switching systems required that a keyboard and later a mouse be connected to the computer As you prob ably know powering up a computer without these peripherals connected would and generally still does result in a boot error message and a failure to subsequently recognize the peripherals if even they are later connected This is why passive switches were awkward one would have to switch to each computer and leave it selected during the boot pro cess a Slow and annoying procedure Some plat forms and operating systems would probe for key board or mouse presence after bootup and if the passive non emulating switch happened to be set so the user peripherals console were assigned to a different computer that probing computer would hang The implementation of active keyboard and mouse emulation services meant that every comput er connected to the KVM switch would get a port response that told the computer it had a keyboard and mouse present even though there was only one on the system In order to perform this func tion the KVM switch was equipped with integrated circuits that interacted with the attached computers as though they were the actual keyboard or mouse only
46. adapter to work with a dif ferent model The newer Sun monitors have both 13W3 and HDD 15 connectors so they work with all Sun computers and with many PCs as well SGI Video Silicon Graphics has specialized in graphics intensive workstations and servers that are widely used in the motion picture industry and elsewhere While the company s focus has been changing recently quite a few of these high resolution wide video bandwidth machines are in use and they often benefit from KVM switching or extension Typically the SGI machines have separate BNC connectors for Red Green Blue and Sync con nections though some may use HDD 15 VGA type connectors Matching the connector is less of a concern than handling the bandwidth Often the video output is not only high resolution but also high refresh rate so the overall bandwidth can be very high For example it is not unusual to see an HDTV or Cinemascope like wide screen format at 1920 x 1200 pixels running at 85 to 100 Hz At 85 Hz this represents a 284 MHz bandwidth We know of only one manufacturer that makes a KVM switch or extension product to handle this high a bandwidth Moreover there can be TWO video outputs per computer in which case the KVM switch must be able to select and assign two video sources again this calls for a special purpose switch So while a manufacturer may claim to be SGI compatible be sure you check the precise specifications of your SGI com
47. al in a fiber as a result of the rays following different paths or modes down the fiber This limits the number of pulses that can be sent per second In multimode fiber larger core than single mode rays take many different zigzag paths along the fiber requiring more time for some signals to arrive at the other end which causes a smearing running together of on off digital pulses mode The path that a light pulse component can take to travel down a fiber modem A unit that transmits digital signals over a transmission medium typically over a telephone line A contraction of modulator demodulator Gen erally modems convert signals from digital format to analog audio format and vice versa Typically modems include circuits and or firmware to handle handshake establishing a specific type of connec tion flow control making sure buffer memory does not overflow and error detection correction 29 motherboard A printed circuit board on which connectors are mounted and interconnections are made with another pc board daughterboard A board to board application with the motherboard usually being the larger and containing other elec tronic subassemblies Page 65 multi console A K V M switch architecture which allows more than one console 1 e keyboard monitor and mouse to access different attached computers at the same time The first such systems were introduced around 1995 multimode fiber A fiber that a
48. also with the particular hardware platforms on which those O S s are running Network environments Novell Netware Banyan Vines etc are NOT O S s but they can impact KVMS operation if someone patches the scan code set Normally the network environment will not matter because the KVMS is not involved in the network end of the connected computers Methods of Switching We have already described briefly the methods of switching direct selection via pushbuttons or displayed menus indirect selection via step up step down buttons direct selection via keyboard com mands and scanning of connected computers in sequence Let s discuss these approaches in more detail To some users direct access to a given com puter is essential They do not wish to wait for the scanning to get to the platform of interest nor do they wish to take the time to step through various platforms with incrementing lt I gt buttons Manufacturers who provide direct access via push buttons on the switch offer the simplest most cost effective approach for direct access However it may be necessary to physically place the switch at a location that is out of convenient reach of the operator This may for instance permit many computer to switch cables to be kept short which saves money and avoids signal degradation and then the only longer cables are those run to the monitor mouse and keyboard since the KVMS can buffer these signals the extra
49. an control as many as 256 computer systems Single Console KVM Switches of Various Capacities Adding a limited degree of extra functionality some KVM switches or add on external devices cre ate a second console output for the same single console switch One should take note of this Dual Access is via one shared bus and does not enable the two user consoles independently select different CPUs as 1s possible with a true multi console KVM switch Instead the same computer system will be viewed simultaneously and can be controlled alternately from the two access consoles Dual Access KVM Switch for Two Users is Not True Multi Console Both Must View the Same Computer Page 16 True multi console systems enable multiple user consoles to connect either to different CPUs in a single chassis or to CPUs distributed throughout mul tiple interconnected KVM switch chassis Multiple consoles typically have access to all computer sys tems via the backbone bus structure of the KVMS system although some consoles may be restricted only to access portions of the overall system by virtue of their installed location within the switch system ae ee ee lt DI PI DE BE BE BL B LD A Basic Dual Console KVM Switch in Which Each User Has Independent Access to Any of The Computers Even if access is potentially available to all CPUs it may be restricted by an administrator Other than a handful of smaller 2 to 4 user mult
50. an be displayed horizontally and vertically on the monitor screen These dots are technically called picture elements or Pixels Color depth refers to the maximum number of colors that can be defined and displayed at once Vendors dis cuss color depth either in bits of data they use to define the colors 1 e 24 bit color or as a numeric value for the numbers of colors that are available 1 e 16 million colors Vertical Sync Frequency which is the same as Frame Rate or Refresh Rate on non interlaced displays and indirectly related to the Horizontal Sync frequency describes the number of times per second the screen imaged is updated refreshed The important factor here is that you cannot mix video cards based on one sync fre quency with monitors based on another unless the monitors are multi sync which means they can synchronize to different video refresh rates and often to different resolutions In today s market place most monitors are of the multi sync variety though they vary widely in rated capability If the screen goes black when your KVMS switches to a particular computer you may have a bad connec tion or a technical problem or it may just be that the computer is putting out a signal which that particular monitor cannot accommodate you can sometimes check this by connecting the monitor directly to the computer s video output if it works in a direct connection then there s a switch system problem
51. ands are slight in comparison to a high resolution computer monitor displaying 1024 x 768 pixels at 72 Hz vertical sync rate That monitor is displaying 56 million pixels for each of 3 colors This requires a video bandwidth of 70 MHz the dot rate for a single color unmodulated a lot of processing power for any computer workstation And if you are using 16 7 million colors that eats up memory too All this explains why TV sets are not generally used for computer display nor can the TV tuner be used as a video switch just in case the thought occurred to you One more potential TV Computer video incom patibility is signal level VGA levels are zero to 700 mV 0 7 volts whereas NTSC is zero to 1000 mV 1 volt Page 32 Other KVMS Factors Operating System Considerations Strictly speaking the KVMS should be inde pendent of the computer s operating system O S After all you hook up a monitor and keyboard to a platform Then you install whatever O S you wish to run DOS Windows NT OS 2 Deskview Mac System 8 or 9 or X the current Mac O S varia tions which are NOT PC compatible Unix Xenix Microsoft s version of Unix etc Why should it matter to the switch what software is installed The simple answer is that the O S should not matter and the switch should not care what oper ating system is in use But simple answers can be misleading We have seen some KVM switches that have had problems with NT whe
52. apable power supplies or even dual redundant power supplies a feature you may wish to look for Reliability issues notwithstanding anything can break and it will or so says Murphy s Law You will want to look closely at the warranty and equally important at the support available from the manufacturer and from the vendor that supplies you with the KVMS You will want to know that replacement product is readily available And you will want to select a product made by a manufac turer who will be around a year or several from now A related issue is whether the product will continue to keep up with technological advances in your computer setup Look for features like upgradeable firmware if you really plan to keep that KVMS for a long time because it s almost cer tain that changing computer hardware and operating systems will demand updated KVMS firmware Make the right choices in these areas and your KVMS will deliver not only initial cost savings but ongoing savings year after year Make a poor choice and downtime can eat up those savings in a hurry Efficiency amp Productivity Less Tangible But Very Significant Sources of Savings Because the KVMS enables an operator to sit or stand in one place while checking tens to thou sands of computers that operator can be much more productive While the KVMS may require a fraction of a second or even a second to change from one computer to the next this is le
53. application with the daughterboard being the plug in usually smaller board Also called daughtercard In some KVM switches optional or updated func tions are installed by means of daughterboards dB abbreviation See decibel de Direct current An electrical current flowing in one direction only dc method A technique of daisy chaining K V M switches The preferred dc method is through dedi cated ports on the KVM Switch chassis whereby an Out Port of one switch is cabled to the In Port of the next KVM switch and so forth Alternately the console user port of one KVM switch may be con nected to the system CPU port of the next KVM switch and so forth to create a daisy chain DEC Digital Equipment Corporation One of the earliest makers of mini computers and software for them DEC subsequently added powerful micro computer based servers and to their product offer ings as well as peripherals such as printers and drives Compaq now owns DEC decibel A unit expressing the ratio of two volt ages currents or powers abbreviated dB One dB is equal to 20 times the common logarithm of the ratio of two voltages across or two currents through equal loads One dB is also 10 times the common logarithm of the two powers One decibel is approx imately the smallest change in audible power that can be recognized by the human ear whereas 3 dB is approximately twice the volume decoder A device used to convert information
54. area Additional management fea tures provide control of security and special mainte nance functions of the KVMS or the entire KVMS system Some of the larger KVMS systems include user tracking set up for dual monitors or port I O control through the OSD The most useful function though is extending the reach and users ability to identify and select computers that are on large KVMS backbones and may even be located in the next room or the next building While the control methods above have all been external to the computers controlled by the KVM Switch the most recent trend is moving towards software The use of software provides the end user with an even better control mechanism The under lying benefits of database software presents an extension to the OSD that can be recorded on a much larger scale One manufacturer has imple mented a control tool that combines hardware and software to manage the actual security authentica tion and selection method This system works inde pendently of the actual switching hardware Yet another product may combine the embedded firm ware and an external software piece to manage security while switching is managed by the KVM Switch hardware In all cases where software is used external or within the KVM Switch you ll be getting a higher degree of tracking features that will help you to manage the KVMS system Emulation Services The primary reason why KVM switches moved rapidly from passive to
55. at 5 cables are generally UTP unshielded twisted pair but some applications utilize STP shielded twisted pair cable which is stiffer trickier to ground has more loss and is not better for most applications A newer standard Cat 5E 1s recommended for gigabit speed Ethernet over copper if fiberoptic is not used cathode ray tube Abbreviated CRT this is the high voltage driven phosphor faced picture tube found in traditional computer monitors television receivers and oscilloscopes CCITT An acronym for Consultative Committee for International Telephone and Telegraph An international standards group central processing unit Abbreviated CPU The section of a computer that contains the arithmetic logic and control circuits In some systems it may also include the memory unit and the operator s console The abbreviation CPU is often used to describe an entire microcomputer including the actual CPU as well as RAM ROM I O ports drives power supply and so forth although this is not technically correct it is a widely accepted shorthand channel The path along which signals are sent the medium can be wire optical fibers or free space characteristic impedance The ratio of voltage to current at every point along a transmission line on which there are no standing waves chip A single substrate on which all the active and passive circuit elements are fabricated by semicon ductor manufacturing t
56. ated by placing the interface in a single KVMS main chassis and instead using KVM extension technology to connect to individual CPUs The size or number of ports a local chassis will support varies from two to sixteen This means that the number of KVMS chassis required to sup port eight servers in a single cabinet will be four two or one Optionally a sixteen port chassis would support enough servers for two to four cabinets typically Of course with larger servers that each occupy a third to half a cabinet particularly if equipped with external RAID systems an eight port KVMS chassis will support two or three cabinets Do your racking and permitted wiring practices sup port point to point cabling across multiple cabinets or do you have to dip under the floor or up to a ladder rack when bridging cabinets In each case the rack layouts and cabling requirements must be planned in great detail if the installation is to pro ceed smoothly Platform Support There is native support for multiple computer platform architectures like DEC Mac Sun SGI and Intel or even ASCII terminals but such support is not present in all KVMS products Advertisements and product brochures promote many KVMS prod ucts for multi platform support whereas in reality native support may apply only to a few types of computers with special adapters being required for support of other types While some multi console KVM switches simply don t provide you with
57. been developed that integrate terminal emulation with direct PC connections These products enable you to reduce a mix of terminals and PC monitors and keyboards to a single or a few consoles In some cases there is a protocol conversion from ter minal mode ASCII RS 232 to VGA PS2 within the switch and in other cases external protocol con verters are employed Additionally it is possible to launch a terminal emulator on a standard PC and to bring that PC into a standard KVM port Since this latter solution is primarily a software add on it can be more cost effective than external converters which typically cost in the neighborhood of 500 per port Switches that are built specifically for terminal control may substantially less per port but don t support conventional KVM systems Switches that support a mix of conventional KVM and terminal connections without external convert ers typically cost about the same as using external converters but are easier to set up and more reliable since there are fewer cables and parts involved Use One Interface to address a Mix of PCs RS 6000 Mac Sun HP Dec Alpha SGI or other Platforms Today s complex network environments often call for a mix of servers including Intel based or clone x86 platforms Macintosh platforms Dec Alpha and or Sun Sparc and Enterprise platforms Video and film effects production facilities often add high power SGI Silicon Graphics processors to the serv
58. board and Mouse Connectors are Identical Mini DIN 6 Type Page 21 Personal System 2 computer PS 2 PS 2 mice incorporate two way communication using 3 byte data packets The first packet defines button state up or down and the subsequent packets define mouse movement X Y The mouse sends syn chronous serial data similar to the protocol used by a PS 2 keyboard in fact the data is handled by the second channel of the keyboard controller It is significant to note that only the movement relative to the prior mouse position is sent not an absolute pixel map location That s why a mouse can become unsynchro nized if there is any inter ruption of its data stream to the computer An unsynchronized mouse with a KVM switch is manifested as a cursor that appears to jump and move around wildly stimulated by but not respond ing sensibly to mouse movement Some KVM man ufacturers do a better job than others of avoiding this condition or allowing the user to fix it quickly when it occurs Combo mice have a male 6 pin Mini DIN PS 2 style connector and a cable adapter that can convert it to a female DB 9 serial Internally the mouse sets itself to transmit serial data or synchronous PS2 data the PC hardware deter mines the mode of mouse operation All currently shipping PC type KVM switches require the use of a PS 2 type keyboard and mouse though most also support computers with serial mouse connecti
59. brid Figure B illustrates a change in the tier three to four connection from Star to Series Series Star and Expanded Star are combined to create the third Hybrid model Figure C In multi console KVMS systems the likelihood of degraded video quality is the primary factor restricting the tier System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Hybrid Figure A Tier 1 left Stars to Tier 2 Tier 2 Stars to Tier 3 and Tier 3 Stars to Tier 4 Page 38 depth Secondarily the KVMS firmware s ability to mum underlying conditions exist the KVMS sys address downstream chassis may also be a factor tem may perform well beyond the stated specifica addressing and naming larger numbers of CPUs tions This is unde
60. ch A mechanical or electronic device used to make or break an electrical circuit synchronize Make sure that the level or pulse is presented to the system or subsystem at the cor rect time With KVM systems mouse or keyboard synchronization assures that motion of the mouse or keystrokes convey the intended controlling bytes of data to the selected computer synchronous A device or system in which all events occur in a predetermined timed sequence Usually all parts operate to a common clock synchronous transmission Transmission in which the data characters and bits are transmitted at a fixed rate with the transmitter and receiver synchronized Page 74 T tactile feedback The feel or snap action of certain constructions of keyboards A new type of mouse is intended to give the user virtual tactile feed back by interacting with elements on the comput er s displayed windows It is unlikely any current KVM switch will accommodate such mice or com puters using the specialized drivers for these mice because special firmware would be required in the switch and the mouse was just introduced in 2000 TDM Abbreviation for time division multiplex ing Tempest A classified Department of Defense program to provide secure electronic equipment through extensive EMC techniques Electro Mag netic Cladding terminal An electrically conductive item designed to be attached to a circuit or device for conv
61. ch connectivity is offered primarily for maintenance access rather than for prolonged remote work sessions The physical con struction of these remote access products is similar Both utilized specially prepared computers running a Remote Host software application Even though these products are pre configured and shipped with a default software selection you actually have options for the access software that these products can handle The access devices are pretty much off the shelf high end Intel processor based com puters with their own hard drive RAM and NT Server operating systems What is different is that the KVMS manufacturers include special digitizing boards that are able to generate KVM signals from the remote client serial data stream so that the remote access device puts out keyboard and mouse signal most computers with remote access software merely respond to remote input while their own keyboard mouse ports are idle The output of the remote access device in turn can control a single computer or the console connection of a KVM Switch where it provides access to any of the switched servers The remote user selects which computer he would like to control either through OSD or a similar software menu See Controlling and tracking User activity on the KVM Switch There are a number of differences in using such remote access devices compared to using a pure remote access software on server approach In this KVM scenario no
62. cified test current Overall con tact resistance would be the wire to wire measure ment continuity A continuous path for the flow of cur rent in an electrical circuit controller An instrument that holds a process or condition at a desired level or status as determined by comparison of the actual value with the desired value core The central part of the fiber optic in which light is actually projected to its destination CPU Abbreviation for central processing unit crosstalk A magnetic or electrostatic coupling which causes the unwanted transfer of energy from one circuit the disturbing circuit to another circuit the disturbed circuit For instance video sent down one cable may appear via crosstalk as a shadowy ghost on another video circuit CRT abbreviation for cathode ray tube CSA An acronym for Canadian Standards Associ ation A nonprofit independent organization which operates a listing service for electrical and electron ic materials and equipment The Canadian counter part of the Underwriters Laboratories in the USA current The rate of transfer of electricity from one point to another Current is usually a movement of electrons measured in amperes milliamperes and microamperes current rating The maximum continuous electrical flow of current recommended for a given wire or circuit expressed in amperes cutoff frequency fe The frequency at which a filter provides 3 dB of los
63. configuration If you combine KVMS with a suitable racking system designed for multiple computers not just bakery racks or warehouse shelving you will save even more floor space while significantly improving maintenance access so it takes less time to service the computers It is common to see floor space requirements drop to from one third to one fourth that of the non switched non racked computer room Page 49 Appendix A Connector Diagrams Pin Arrangements are Shown from Mating Side of Connectors Not to Scale N C CLK i D 5v GND DATA N C 6 5 CLK 3 GND Ol lt h N C 2 1 DATA PWR IN KBD 6 XMT KBD 5 RCV a tay 4 MOUSE 01 N 2 1 GND GND GND 4 3 5v D 7 POWER DATA g IN PC AT Keyboard 5 Pin DIN Female in Chassis PS 2 Keyboard same as the PS 2 Mouse 6 Pin Mini DIN Female in Chassis Sun Keyboard and Mouse 8 Pin Mini DIN Female in Chassis ADB Mac Keyboard Mouse amp More 6 Pin Mini DIN Female in Chassis USB Type A Universal Serial Bus Keyboard Mouse etc 4 Pin USB Type A Receptacle for Mating to Chassis or Ext Cable USB Type B Universal Serial Bus GND DATA Keyboard Mouse etc 4 Pin USB Type B Receptacle for Mating to Chassis not for Ext Cbl MOUSE CLK 6 5 KYBD CLK Newer Style 4 3 GND SGI Keyboard 5v and Mouse i 6 Pin Mini DIN MOUSE DATA KYBD DATA Female in Chassis K Ko a
64. d Keyboard Video Mouse User Chassis Dedicated Keyboard Video Mouse User Chassis Dedicated Keyboard Video Mouse User Chassis Page 39 ing for It may take longer than a day for an integrator to configure two or three products but you stand a better chance of gaining an insight into the best products and architecture for your application Smaller KVMS systems based on the Star model are straightforward easy to configure and they install quickly The components are usually com prised of individual KVM switch chassis plus a variety of cables They have a pre configured fixed port design ranging in capacity from four to eight twelve or sixteen ports accessible by two to four consoles They include a means to expand by inter connecting the chassis usually from the console ports of one unit to the system ports of another A complete system includes a user console and system computer interface chassis though these functions may be mixed within the same chassis System Chassis Multi Console Keyboard Video Mouse System Chassis KVM Hub Multi Console Keyboard Video Mouse Router Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi C
65. d on the method and conditions of test The significance is that a material with high dielectric properties may still fail to insulate if the voltage involved is sufficiently high differential mode EMI Interference that causes the potential of one side of a signal line to be changed relative to the other side the type of inter ference in which the interference path is wholly in the signal transmission line digital circuit A circuit typically having two states on or off value 1 or 0 as contrasted to an analog circuit whose output is continuously variable linear Digital circuits transfer or process only numbers even if they are used to represent other things whereas analog circuits may transfer or process a variety of continuously variable or modulated signals digital to analog D A converter A device which transforms digital data into analog data by translating a digitally expressed value to a repre sentative voltage level Typically used for convert ing stored or processed video or audio waveforms into to displayable video or playable audio Also known as a DAC DIN abbreviation for Deutsche Institut fur Nor mung A West German standards organization DIN connector Any connector conforming to DIN standards although often referring to a circular DIN connector popular in audio applications There are dozens of connected related DIN standards For example computers DIN defines many keyboard and mouse co
66. des which tell the computer which key is being actuated Each keystroke actually generates two scan codes one on key down the other on key release The keyboard BIOS in PC AT class machines or the main BIOS in PC XT class machines translates the scan code pairs into ASCII characters This lets KVMS manufacturers use unusual key sequences such as NUMLOCK gt or CTRL CTRL or SHIFT SHIFT to initiate channel switching or other special func tions Some keyboards have unique features that render them incompatible with certain computers and incompatible with certain KVMS too Note that the A in ASCII is American Unicode is a newer character coding scheme that has been introduced in recent years It is designed to support more non English languages and you Page 11 can expect changes in KVMS products to support unicode based keyboards and operating systems if this scheme becomes popular If you must accom modate a unicode based computer or keyboard be sure to ascertain whether the KVM product under consideration will support it While the mouse or trackball which is simply an upside down mouse that stays in one place has always been essential to use of the Macintosh operating system it was not mandatory for PCs and in fact had no function in the PC s initial operating system DOS Because mice were introduced after the original PCs had been built mouse capability was initially
67. distance between the switch and the com puters or between the switch and the monitor and keyboard A few products use fiberoptic technology light transmitted along glass fibers instead of elec trical signals in copper cable to extend the switched distance to thousands of feet such switches are more expensive It is possible to add long distance keyboard video mouse extension devices to switches that don t otherwise support long cables read about extending the distance in KVM Extenders Page 15 Single and Multi Console Switches Many brands and models of active KVM switch es the focus of this paper are currently marketed Aside from the issue of single bus or multi bus con trol paths there are differences in physical construc tion functional capability cable interconnect and methods of control Single bus KVM switches provide a single path through which the switching services connect an external monitor keyboard and mouse to any one of the attached computers Equally they provide a concurrent input data path for connecting keyboard and mouse signals to the selected output of the port being displayed on your monitor In all current single console KVMS implementations the switch Input Output I O instructions are hardware resi dent and require no software to be installed on the switched computers Multi console KVM switches differ widely in their approaches to routing KVM signals among multiple consoles See the
68. distance on this side of the switch does not necessarily cause any deg radation With the switch out of reach however another method of computer selection must be pro vided Keyboard controlled switching is one obvious answer allow command keys or an escape sequence activated series of hot keys to select the computer being accessed As implement ed widely today there is no need to modify the soft Page 33 ware on the various computers to effect keyboard switching you want the operation to be seamless to the computers Another approach is to provide a remote control for the KVMS some manufacturers do this but the feature can be more costly than use of keyboard access and it places another piece of proprietary equipment on the desktop On the other hand a remote control avoids any chance of accidentally issuing an incorrect command to a given computer when you had intended to issue a switching command In some cases a remote can save money by allowing the switch itself to be closer to the CPUs Here multiple short CPU to switch cables and one long switch to remote cable may be used instead of multiple long cables In reality remote controls are most often used for specialized environments where there may be no access to a conventional keyboard 1 e point of display systems sales kiosks etc A more recent and now widely available remote or local switch approach is the on screen display OSD or menu
69. driven switch interface Most of the OSDs today are similar in appearance and there has been litigation between competitors over this issue but appearances are not the key issue For example in some KVMS systems the OSD will not be visible unless a given CPU is already selected and is generating a video signal in this instance the OSD uses the computer generated Sync signal to throw up its message The problem is that some computers will go to sleep and not put out any sync or they may be shut off and if you then have to rely on the OSD to select another computer you re out of luck You may have to switch in the blind just to get any OSD at all then select the CPU you really wanted to control Some OSD equipped KVMS systems also provide for access security system analysis and other special functions There are obvious differences in the image quality and the nature of displayed information but you have to look beyond the mere naming of CPUs to see how well an OSD works You may also wish to examine special features to see if they are important to you Some switches for example offer a Broadcast Mode in which key board commands can be sent simultaneously to mul tiple computers This may save time when issuing shut down commands to a rack full of computers in the event of an emergency or for simultaneously initiating routine backup loading new software and so forth Some KVMSs that provide for automatic scanning of
70. ducts and switching allow expensive graphics platforms like SGI and Avid platforms to be located securely in an easily maintained machine room with their control selec tively deployed to those studios in which they are required High resolution KVMS and extension systems with the possibility of multiple video con nections per CPU support these demanding appli cations Page 7 Page 8 Video Keyboard and Mouse Circuitry A Non Technical Overview To understand how switches function it is help ful to understand something about video and key board circuitry In the following paragraphs you will find an overview of the types of video signals and what the various acronyms mean You will also learn a little about keyboard functions and how switches and computers deal with the key board Relax you don t need to know much about electronics or math to comprehend this discussion Monitor keyboard and mouse functions are gener ally transparent to the user and only matter when you are purchasing components assembling a sys tem and initially setting it up They do matter to the switch though as you will learn If you want to know more about these video and keyboard functions see Product Function for the Technically Oriented Reader Video Three primary considerations for handling video signals are the resolution color depth and refresh rate or sync frequency Resolution describes the number of dots that c
71. e ARE you going to put the file cabinet The guest chair The answer is to use KVMS An economical 4 port keyboard video switch 150 to 800 depending on the platforms support ed user interface physical construction expand ability etc plus cables enables the developer to place a single monitor and keyboard on his or her desk in a comfortable easy to use position There is still room for reference documents a telephone even a photo of the family For the developer who is operating a large lab the benefits of KVMS are substantial Space savings and increased productivity due to operator comfort are clearly justifications for KVMS in the developer s office KVMS also reduces one s exposure to electro magnetic and electro static radiation While recent revelations of fraud in earlier studies undermined arguments about the dangers of such exposure the actual hazards associated with ELF and VLF fields Extremely Low Frequency and Very Low Frequency remain unknown Do they lead to metabolic changes on a cellular level Do they cause cancer Do they cause eyestrain While the answers are arguably inconclu sive it is certain you will reduce the direct exposure to a potential hazard by reducing the number of monitors in close proximity to the operator For the developer who is operating a large lab the benefits of KVMS are substantial You will save a huge amount of floor space in some cases making the difference bet
72. e The more advanced implementa tions of this technology may support additional sig nals including stereo microphone and speaker data as well as serial data These products function by compressing and or multiplexing data at one end of the link and transmitting from end point to end point over a single cat 5 then decoding the data at the other end Category 5 Cable Usage in KVM Products Category 5 is a standard for construction and performance of telephone or network cables Cat 5 UTP Unshielded Twisted Pair cables have four twisted pair of copper conductors and the cables terminate with 8 pin modular telephone style RJ 45 male connectors Shielded Cat 5 cables exist but are not generally used in KVM applications be sure to check the manufacturer s spec for a given prod 50 to 1000 Ft epending on System Receiver D Q O LO gt O O O Page 44 Category 5 Keyboard E Monitor Mouse f 2 Port KVM Switch KVM Cables PS 2 VGA Category 5 Transmitter Typical KVM Extension Product Used Here to Locate one Computer at a Distance from the KVM Switch other Computer s and Console uct Also some cables are wired straight through whereas others are wired for crossover the latter having certain conductors switching position on one of the RJ 45 connectors You cannot interchange straight through and crossover cables and if you inadvertently use the wrong one in certain K
73. e or random changes in shift lock states as KVM signals experi ence out of sync conditions You may not even be able to use a certain computer with a certain KVM switch That is why KVMS systems should include support for firmware updates whether via plug in ROM or flash upgradeable ROM Firmware updates though are not a magic bul let You don t want to HAVE TO install new firm ware every few months because a KVMS maker neglected to account for this or that variation in products As a rule the KVMS firmware will change less often than the operating system is updated In the authors experience many well made KVMS systems have been in service for years before requiring any firmware changes Be sure to look into this aspect of the system you re consider ing Capacity and Scalability Through out this documents we briefly mention the capacity of some of the available products This section provides you with a comprehensive look at the range of sizes and what you can expect from a KVMS system in maximum capacity The smallest multi console KVM Switch is a simple two console by two computer switch each console can select between the two ports The largest multi console KVM Switch in a single chassis supports eight con soles on a backplane that supports thirty two com puters There are many variations in between and the most common chassis sizes you re likely to encounter will support four eight twelve or sixteen computers acc
74. e mean by KVM Extension Engineers responded to the need for longer dis tance extension beyond 25 or 50 feet by develop ing specialized electronic devices which we charac terize as KVM Extension Products In most cases these devices are comprised of a transmitter at the computer or KVM switch and a receiver at the keyboard monitor mouse location These devices employ special active signal processing with local loop back and or impedance conversion to avoid timing problems with keyboards and mice They also use video line driver amplifiers to deliver video to the monitor at greater distances while avoiding excess quality loss Some KVM extenders require specialized cabling possibly even fiberoptic cable while a number of more recent products utilize ordi nary Category 5 Cat 5 network cable Various brands and models of KVM Extenders are built to work over different distance ranges the case with KVM switches you need to test a given extender with the particular devices you wish to extend to be sure it will work satisfactorily in your application always ask for a money back or exchange guarantee KVM Extension Products make a very useful adjunct to a KVM switch system allowing certain computers or user control consoles to be placed at a greater distance from the switch than would otherwise be possible Moreover KVM extension products can provide greater security in that they allow one to keep those switch components that mig
75. e speci fied to be 84 inches tall and 44 RU while 44 x 1 75 inches is 77 inches that represents the usable rack mounting space whereas the 84 inches represents the overall external height S safetying A term used to cover the use of product features designed to prevent the loosening of hard ware or other mating elements under conditions of shock and vibration Elements drilled for safety wiring would be an example of this type of feature In a very general sense a locking connector is a means of safetying a KVM cable to the switch scanner An electromechanical or electronic device normally cyclic in nature with N number of steps starting at a predetermined point and return ing to that same point Scanning in a KVM switch refers to the automatic switching from one CPU to the next without user intervention this is useful for casual monitoring of multiple systems as on a large display monitor schematic A scheme for presenting information Thus a circuit schematic in diagrammatic form indicates the components wiring and connections of the circuit Schmitt trigger A bistable trigger circuit that converts an input signal into a square wave output signal by switching action triggered at a predeter mined point in each positive and negative swing of the input signal Schottky TTL A type of TTL transistor transis tor logic notable for faster operating speeds than standard TTL scratch pad memory
76. e use of ground breaking adap tors or optional power supplies can reduce or elimi nate this noise sometimes an additional device to device chassis ground conductor is useful H handshake A multistep connection routine A ver ification by the central processing unit that a com puter data terminal has correctly identified itself and all systems are ready to initiate communication Also used in modem connections to verify that sys tems are ready to receive data or more data Henry Unit of inductance hermetic Airtight impervious to external influ ence as in a hermetic package Often used to describe metal to metal solder or weld sealed pack ages In reality all materials are permeable hence specifications define acceptable levels of hermetic ity Hertz Term for cycles per second by international standard adopted and now common in U S From the German physicist s name Heinrich R Hertz In use we find that 60 cycles second or 60 cps becomes 60 hertz or 60 Hz hexadecimal A numbering system with the base 16 The digits of the system are 0 1 2 3 4 5 6 7 8 9 A B C D E and F The addressing of some KVM switch systems rely on hexadecimal coding horizontal sync The synchronization frequency at which the video beam sweeps across the face of a monitor to paint the pixels of each line Typically measured in thousands of Hz hybrid A blend or composite of two different technologies
77. e video keyboard and mouse signals separately In one case there are actually up to four separate switch chassis one each for video keyboard mouse serial and audio function if there are no audio or serial requirements the respective chassis need not be purchased In another instance the matrix type switch chassis employs a four teen layered motherboard backplane all connect ed CPUs apply video signal to that backplane at all times In this system the video is routed to user console ports on demand and a short while later the keyboard and mouse control is assigned to the console port pending authentication of that user s admuinistratively assigned level of access t t W p t y 4 gi iP rp ut yt of oP of cpl g Wy ye Ww Ta ARAN V Y OOP oF USER t t P p yt x CONSOLE d t J 3 mne pe We u j JF y6 yI g g F y fl pu N P VK MV K MV ut y M N Split top vs Unified Architecture bottom KVMS Single Console Versus Multi Console and Multi Access Single and multi console KVM switches serve similar purposes their unique attributes and capa bilities determine which will best serve in a given application A single console KVM switch provides one console with simple access to one bank of com puters typically numbering 4 6 8 12 or 16 These single console systems usually allow for con necting multiple chassis in a daisy chained or star configuration whereby the same single console c
78. eater distance from the computer than would otherwise be possible using conven tional cabling Typically conventional cabling is not usable for more than 10 to 20 feet Extenders incorporate special electronics to allow that dis tance to be stretched to greater distances Copper cabled extenders yield distances of 300 to 800 feet dedicated copper cables or ordinary Cat 5 cables depending on the model and fiber optic cabled extenders can go as far as 1 to 2 miles depending on the model and type of fiber used Extension Products See Extender Page 60 F f Symbol for frequency Farad Unit of capacitance feedback The recycling of a portion of an output to the input of the circuit positive feedback Recycling of a signal that is in phase with the input to increase amplification Used in digital circuits to standardize the waveforms in spite of any anomalies in the input A pat on the back negative feedback Recycling of a signal that is 180 degrees out of phase with the input to decrease amplification Used in linear circuits to stabilize performance and minimize distortion Thumbs down ferrule A short tube Used to make solderless con nections to shielded or coaxial cable When made of a magnetically absorbing compound such as ferrite the ferrule can serve as an RF radio frequency filter element Often ferrite ferrules of about 3 4 inch diameter by 1 1 2 inch length are seen on video monitor cabl
79. echniques Its function can be simple or complex Often used interchangeably with IC integrated circuit circuit 1 A complete path through which elec trons can flow from the negative terminal of a volt age source through a conductor and back to the positive terminal 2 The interconnected combina tion of a number of elements or parts to accomplish a desired function e g filter switch amplifier circuit element A basic constituent of a circuit exclusive of interconnection CISC An acronym for complex instruction set computer The alternative to a RISC system Typi cal CISC CPUs include the entire Intel x86 series and the Motorola 68000 series cladding An outer layer on a fiber optic core which promotes total internal reflection of light and also serves as a protection medium clear To replace information in a storage device or register by zero or blank in some machines Also frequently used as being synonymous with reset even in cases where neither memory nor counters are involved clock The device in a digital system which pro vides the continuous train of pulses used to syn chronize the transfer of data A clock circuit is generally built using a crystal oscillator for stability Page 55 CMOS An acronym for Complementary Metal Oxide Semiconductor Also refers to popular MOS integrated circuits that use both p type and n type material for the channels This allows very dense packaging a
80. ector which was widely copied Later with the PS 2 series circa 1987 IBM changed to a smaller mini DIN Deutsche Industrie Normen a German stan dards organization 6 pin round connector Today various clone manufactur ers use AT or PS 2 style keyboard connectors and some manufacturers vary Original AT Style or DIN 5 the keyboard connector Keyboard Connector from model to model A few models have both types of connectors although the second type may be hidden behind a knock out in the com puter case Finally in late 1998 through early 1999 some computer manu facturers began shipping products with USB uni versal serial bus keyboard PS 2 Style or Mini DIN 6 j Keyboard Connector Same connections and only NOW Type Also Used for Mouse are KVM makers begin ning to support USB key board and mouse USB to PS2 or ADB Mac converters are inexpensive workarounds when there is no direct USB support While adapters also can be used to change from AT pin configu ration to PS 2 configura USB Universal Serial Bus tion or vice versa there A Type Connector for are electronic differences Keyboard Mouse and Many between some computers Other Interconnections that are not so easily con verted the so called key scan codes may differ too The original IBM PC XT keyboard scan set was developed by a student and was anything but elegant The subsequent AT keyboard command set was based on the XT and
81. ee 10 NISC VidCO cea neueataon E e 11 e Keyboards Mice Wheel Mice Trackballs Trackpads Q Q 11 How Does a Keyboard Video Switch Work ccc c ccc 12 e Passive Versus Active SWItCheS cm t ae ae io a ho karena notte hehe vee kaso dee hand ba ees 12 How Does the Active KVS Wotk c scse ped deme 4005 id auie iJon edad bd d a a l bed l s le c n 12 Single and Multi Console Switches c cc ccc ccc 15 e Unified Versus Split Bus Architecture c ccc 15 e Single Versus Multi Console and Multi Access eee eens 16 e Single Versus Multi Platform KVM Switches cc 17 Product Function for the Technically Oriented Reader QQ 18 Keyboard Switching passe eee 424 bene 6 EE Mc a AE se bee ete eee en eee ee 18 e MouseSWitchiNg c c 20 History Or Ine MOUS tise tw eho ee he i Pee eee ee hee 34 E eee ee 20 USB Connections sa4c5 500544 526 oa oe abd eise 00802 EEG has ORES m NE a ERG Sete YG ORES 22 e What it takes to deliver a Good KVM Switch c c Ze AVIdeoRefreshef c c 24 Color DOPE og a ak ob ee oh oa aA bh Os e 1 01 RAS h Dobol rne oe Os a A 24 SOG gaxarteges saan hoe erase pee naee heed pae hace yaa sued AAA 24 e KVMS Video Signal Processin ao c 665545 i u nie ob i n ee 465 R Grua Oboe red oe nrl e e 25 e Monitor Types amp Standards
82. egacy ADB PS2 and AT type connections in favor of more stable future looking USB connections There is absolutely no inherent compatibility between a USB based key board or mouse and a conventional one so a tra ditional KVMS won t work with these devices Fortunately though many of the USB equipped computers also have conventional PS 2 PC or ADB Mac ports that do work with today s KVMS If not a variety of USB adapters are available for about 50 to 100 each that convert USB to PS 2 or ADB connections and coding these are 1 way adapters so be sure to get the right one if you need such a unit Ultimately we will see KVMS manu facturers offering USB equipped switches This will be beneficial because USB is actually a much better defined standard and therefore promises greater universal compatibility than traditional keyboard and mouse standards Serial terminals use several different standards for keyboard coding and connectors They do not use mice Teletype machines TTY originally used a 5 bit Baudot code which later evolved into ASCII 7 bit code which was then picked up by early CRT displays These were commonly known as glass teletypes The ANSI code American National Standards Institute defines the character sequences to do things such as switch to high intensity blink underline and position the cursor on a glass teletype DEC Digital Equipment Corporation used a slightly different ASCII code
83. ement We discuss the control methods and security implemen tations here in a brief review of the industry s options Most early KVM Switches had pushbuttons on the front panel to select the various connected computers Later keyboard hot key sequences were added to allow a user to control switching between ports without touching the switch Hot keys were a Page 41 welcomed solution for consoles that used extension devices to position the console remote to the switch but it often required the users to maintain long list of the computers and where they were posi tioned Both of these methods are still available in KVM Switches and more manufacturers have installed front panel buttons on newer models One company had an early insight and produced the industry s first On Screen Display OSD while another manufacturer developed special mainte nance features both which are accessible through the embedded firmware The later two features have proven to be valu able functions for the end user and invaluable to the latest products More than fifty percent of the products available today include the OSD as a stan dard feature and even more products offer it as an option The On Screen Display allows the consumer to access and select computers by name OSD uses an overlay that is generated by the switch and dis played on the console screen It is independent of computers on the switch or the peripheral hardware at the users work
84. enience in making electrical connections Also a data ter minal typically a CRT with character generator drive circuitry to display text from an serial ASCII data stream plus a keyboard to send ASCII serial data back to the controlled device or system terminus A part of a fiber optic connector analo gous to a contact time delay A circuit that delays the transmission of an impulse a definite and desired period of time time division multiplexing A technique used in data communications technique for combining several lower speed channels into one transmission path at higher speed in which each low speed chan nel is allotted a specific position based upon time in the signal stream tinning A hot dip process for the application of solder coating on conductors and terminals primar ily for minimizing in process oxidation and enhanc ing solderability Cables provided with tinned leads are ready to be soldered but do not yet have attached connectors toroid A coil or transformer wound on a donut shaped core The toroidal core gives a maximum magnetic field within itself with minimum mag netic flux leakage externally track The portion of a moving storage medium such as a tape disc or card that contains the encoded data transients Undesirable voltage and current surges that are usually caused by capacitive or inductive energy discharges in electrical circuits TTL T2L Transistor transistor logic A
85. er or workstation mix Conventional Page 6 KVMS systems have been available to switch any one of these platforms but until a few years ago you would still need at least one monitor keyboard and mouse or other control device for each of the different architectures Today several KVMS products include the nec essary conversion capability so that a single moni tor keyboard and mouse can be used to control a combination of PC Mac Dec HP and Sun plat forms There may be some restrictions as to specifi cally incompatible models so be sure to check care fully to ensure your computers are supported by a given switch model and if they are supported ask whether external converters are required or if support is native which means built in Some KVMS products also enable you to add serial termi nals to this mix The benefits of reduced monitor and keyboard count space savings power savings ease of con trol thus encompass the broadest range of plat forms You also avoid the need for a proliferation of different keyboards and mice which typically are the most difficult peripherals to actually locate comfortably within a given user s reach Office Settings Gain Security and Save Space with KVM Extension and or Sharing The KVM extender can provide excellent securi ty and save space in offices Instead of placing doz ens to hundreds of workstations in crowded office cubicles a number of enlightened faciliti
86. es and IS managers are moving the workstations into closets or even into the data center itself They efficiently and securely rack up the workstations in data cabi nets and use KVM extenders to throw the key board monitor and mouse out to the offices Since only a single piece of Cat 5 cable is needed per office drop Often existing ethernet connections can be re deployed for KVM extension Then the con nections from workstation to hub are easily replaced with short Cat 5 cables at the workstation rack thus avoiding any need for pulling new cables through the facility With this centralized architecture theft of chips or entire workstations drops to near zero installa tion of unauthorized software is less likely and theft of data is reduced Unless a worker has a need to frequently install media in the workstation he or she won t miss the CPU they Il instead applaud the quieter cooler less crowded office While it may cost 400 to 900 to install the extender the payback is worthwhile and can be immediate Extension provides additional convenience in multi shift operations where a given office can be patched or switched to a different workstation That same extended KVM connection can go to a switch in the data center where the person in the office may be given administrator restricted direct access to additional workstations and or servers In studio production post production environ ments extension pro
87. es to reduce radiation of interfer ence from within the monitor though the cable and out to nearby circuits fiber optics A technology in which light is trans mitted through an optical fiber typically a glass fiber Most often used as a transmission link con necting two electronic circuits filter A network of resistance capacitance and inductance designed to pass certain frequencies and attenuate all others The main types are low pass high pass band pass and band reject Also refers to certain software routines that block or reroute digital data based on specified criteria firmware Software in hardware form as for example KVM keyboard and mouse emulation rou tines in ROM flange A projection extending from or around the periphery of a connector and having holes that provide for mounting the connector to a panel or to a mating connector flash memory a form of EEPROM which can be reprogrammed in place within its final installed device by means of a program file which is direct ed to it This differs from a conventional EAROM or EEPROM that must be removed and placed in a special ROM burner device in order to be repro grammed Flash memory flash ROM is used to store firmware in an increasing number of KVM switches making it easier for users to keep their equipment up to date once installed floating ground A grounding technique in which circuit grounds return paths are isolated from earth g
88. essible by two to four consoles Many of these chassis designs are depicted in the section on System Architectures Complete multi console KVMS systems starts with a capacity of thirty two computers accessible by as many as sixteen consoles The highest support available in a single KVM Hub or KVM Switch is one hundred and ninety six computers accessible by sixty four consoles You will find that most multi console KVMS systems can be cascaded to expand the systems overall capacity The Limited Star topology is the most restrictive but KVM sig nals from various banks of these products can be combined at the users desktop using a single con sole KVM Switch Manufacturers are making many advances in their technology and we have noticed new product releases that are installable as an inde pendent system or combined with a smaller system offering a valuable scalability A midrange system might support four consoles to two hundred and fifty four computers while the largest KVMS sys tems can support well over three thousand comput ers with as many consoles as one might imagine The final capacity for the largest systems might be dependent on the User Access ratio There are design approaches that allow you to place eight to sixteen computers accessible through two or more data paths established that would be established between the distributed hardware These systems Page 43 can support over three to four thousand computers attached to t
89. ey higher resolutions won t travel as far sat isfactorily Until recently only one option glass fiber existed for transmitting KVM signals over greater distances Fiber systems can deliver KVM data from 1 000 to 10 000 feet This is a costly solution in just the hardware alone and organiza tions still spend additional dollars to run glass cable between end points Fiberoptic Cable for KVM Extenders Fiber optic based KVM extenders can transmit keyboard monitor mouse audio and other serial data signals over glass fiber As many as three man ufacturers offered these products in the past but only one viable product survives and it carries a high price tag The other two products have either been taken off the market or are not compatible with most of the available switches The survivor is the only product that has cross compatibility with most of the different KVM Switches though not with all of them Remote KVM Access Via Network or Dial Up The latest technology as refined in 1999 by two different KVMS manufacturers allows remote con soles to connect to a single computer or to multiple computers on a KVM switch via the network back bone for cross campus access or through an out of band dial up connection for wider area remote access In its current state however this new tech nology does not yield video resolution great as can be obtained with fiberoptic and the mouse response is noticeably sluggish su
90. gation delay times of the red green and blue signals traveling in different pairs of wires within an interconnect cable generally causes video degra dation as cable lengths increase protocol A formal set of conventions or rules governing the format timing and error control to facilitate message exchanges among electronic equipment prototype A model suitable for use in complete evaluation of form design and performance PS2 Personal computer System 2 the second generation of IBM personal computers after the short lived PS1 More generally PS2 refers to the type of connectors used for keyboard and mouse ports on most of the PCs manufactured in the late 1990s A mini DIN 6 pin connector These are gradually evolving into USB universal serial bus ports instead pulse A change in the level over a relatively short period of time of a signal whose value is normally constant Example The voltage level of a point shifts from 0 to 12 volts with respect to ground for a period of 2 microseconds Pulses can be noise or they can represent the l s and 0 s of digital logic pulse broadening The spreading or lengthening of a light pulse in fiber optic cable due to modal or spectral dispersion pulse width The length of time that the pulse volt age is at the transient level Electronic pulse widths normally are in the millisecond 1079 microsecond 10 or nanosecond 1077 range PVC Abbreviation for poly
91. ge multiplied by effective current then multiplied by the circuit power factor There are 746 watts in 1 horsepower wattage rating A rating expressing the maximum power that a device can safely handle continuously wavelength The distance between two points which are in phase on adjacent waves It is the distance traveled by a wave in a time of one cycle Electromagnetic waves both light and radio have a speed in space of about 300 000 000 meters 186 000 miles per second Thus wavelength in meters is equal to 300 000 000 divided by the fre quency wave soldering An automatic soldering method whereby the molten solder is pumped from a reser voir through a spout to form a head or wave A circuit board is then passed over the wave by a conveyor and all components and leads are almost instantly soldered in place by the wave of molten solder Previously applied resist a chemical coat ing prevents solder from adhering where it is not wanted after soldering the resist is washed off Winchester disk A type of hard disk drive in which the read write head is held a few millionths of an inch above the disk whenever the disk is spin ning and the head is moved laterally by a voice coil type solenoid wire A single bare or insulated metallic conductor having solid stranded or tinsel construction designed to carry current in an electric circuit wire size See American Wire Gauge and circular mil area Wire W
92. giT These characters in system computer language signify on and off 1 and 0 Word length memory capacity etc can be expressed in number of bits black box A term used loosely to refer to any assembly or subassembly usually electronic that can readily be installed or removed from a specific location in a larger system by an operator not famil iar with its detailed internal structure BNC Series A radio frequency connector covered by Military Specification Mil Spec It has an impedance of 50 ohms and is designed to operate in the 0 to 4 GHz frequency range BNC is a quick connect disconnect system using a pin and cam bayonet coupling braid A weave of metal fibers used as a shield covering for an insulated conductor or group of insulated conductors When flattened it may be used as a grounding strap breakdown voltage The voltage at which an insu lator or dielectric ruptures or at which ionization and conduction take place in a gas or vapor broadband EMI Interference electro magnetic interference generated over a wide range of fre quencies EMI sources such as electric motors can induce noise in various circuits or cables through inductive coupling broadband signal A signal transmitted by being modulated onto a higher frequency carrier wave B amp S Brown amp Sharpe Gauge a wire diameter standard that is the same as AWG Page 53 buffer A device or circuit element which sto
93. h right and left Use Ordinary USB Connectors side to accommodate a mouse The physical con nection is via a DB 9 9 pin connector which has separate keyboard trans mit and receive data lines as well as a mouse trans mit line Some newer SGI platforms have a mini DIN 6 keyboard connector on the CPU board but it is wired to handle keyboard transmit and receive as well as mouse transmit unlike PS 2 standard systems where the same physical connector is dupli cated one for mouse and another for keyboard A number of SGI systems also utilize serial connec tions for graphics tablet input and these may be via DB 9 or mini DIN 8 connectors Ultimately while robust emulation is a valuable asset fora KVMS there may not be a way for your switch to comply with certain non standard keyboards or mice trackballs other pointers Mouse Switching We have already discussed the bus mouse serial mouse PS 2 mouse Sun mouse and Mac mouse Each uses a different connector and driver Switches that do accommodate mice must emulate the mouse back to the computer even when a given CPU is not being addressed in order to avoid operating system or applications failure It is true that Macs do not require mouse emulation and PCs can operate with keyboard commands replacing many mouse move ments but if the O S calls for a mouse you ll want to have one that s usable The KVMS may be Page 20 designed to allow more than one type of mouse t
94. he backbone of a large scale KVM switch system If the design specification dictates a one to one ratio you might only get two to three thousand computers on the backbone Obviously only the largest data centers need to be concerned about these capacities but there will be price range issues associated with the two approaches that we discuss shortly Extending the Distance Local and Long Distance We briefly discussed the generalities of KVM Extension Devices earlier in What Are KVM Extension Products Here we discuss the details of KVM Extension Devices because increasingly they may comprise a substantial portion of a KVMS system s technology rThe original KVM extension technology used bulky PVC jacketed shielded cable for the transport medium These became largely obsolete when Category 5 Extension products came to market because Cat 5 cables were non proprie tary widely available in different lengths and easier to pull The original Cat 5 extension products used two Cat 5 cables to transport keyboard monitor and mouse signals Dual Cat 5 technology is still in use to maintain legacy compatibility within some product lines it passes keyboard and mouse over one Cat 5 and the video over another Cat 5 1f audio signals are conveyed they may share the keyboard mouse Cat 5 or travel on yet a third Cat 5 cable The newest technology transmits a minimum of key board monitor and mouse signal data over a single category 5 cabl
95. he desired signal Loosely any disturbance tending to interfere with the normal operation of a device or system Classes of noise include burst or popcorn noise intermedi ate frequency noise at low audio frequencies white thermal noise etc Signals from power supply or ground line coupled into an amplifier output may be considered noise NO or NC contacts Normally Open or Normally Closed meaning the state of the contacts when the control circuit is not energized These terms are most often used in describing switches and relays NTSC Acronym for National Television Stan dards Committee the organization that set the stan dards for television signal formats in the United States of America Similar to the function of PAL or SECAM in other countries O ohm The unit of measurement for electrical resis tance A circuit is said to have a resistance of one ohm when an applied emf of one volt causes a current of one ampere to flow on screen display see OSD operating system An organized collection of techniques and procedures for operating a com puter Specifically a software package defined to simplify housekeeping and such routine chores as input output disk reading and data conversion Page 66 operational amplifier op amp Originally an amplifier to perform mathematical operations An amplifier with two differentially connected inputs with high voltage gain and with one output which ideally is a
96. he fly device changes and auto recognition Computers that support USB connec tions generally allow for USB type keyboards and mice but may also be connected via USB to a com patible printer video or storage media CD drive etc The type of devices that can be supported are determined by the USB specification and within a given computer by its own USB support database USB is not well suited for hard drives because the bus is not fast enough to handle the data transfer rates of today s hard drives The USB Universal Serial Bus keyboard or mouse is not yet supported by more than a few small scale KVMs though this may change in the future so ask us or the KVM manufacturer if you have USB keyboards that must be accommodated Don t confuse a bus mouse with a universal serial bus mouse The Bus mouse as explained previously was an older standard something like a serial mouse but it interfaced to a PC using a dedicated interface card The USB mouse uses one of two standard USB connectors that have no pins but rather a mating slot with multiple conductive fingers The current USB 1 1 standard is about to be superceded by 2 0 Within USB 1 1 there are actu ally two standard connectors A and B The slot shaped A standard is used for patching connections it may be located on a chassis or in line between 9 Page 22 two cables It has a male plug that measures 4 5 mm thick x 12 mm wide 0 17 x 0 47
97. he input may be dc or ac the output serial or parallel binary or decimal ADC See A D converter address A specific location where data is stored in a computer circuit memory a numerical or alpha betical designation of the storage location of data alphanumeric Code structures using letters and numerals often with added special symbols am amplitude modulation Modulation in which the amplitude of a wave is the characteristic subject to variation American Wire Gauge Abbreviated AWG Numerical descriptor system for wire size based on specified ranges of circular mil area American Wire Gauge starts with 4 0 0000 at the largest size going to 3 0 O00 2 0 00 1 0 O 1 2 and up to 40 and beyond for the smallest sizes ammeter Instrument designed to measure current flow in amperes Available for either alternating or direct current A milliammeter measures current flow in milliamperes and a microammeter in micro amperes See galvanometer amp abbreviation See ampere ampere Abbreviated A or amp Practical unit of electrical current the current flow rate 1 e quan tity of electrons passing a point in 1 second One ampere is one joule of electrons moving past a point in one second A potential of 1 volt will send a current of ampere through a resistance of 1 ohm amplifier A circuit device or component which provides an output signal essentially identical to the input signal but at a
98. he input signal to the second amplifier and the output of the second to the third and so on Each amplifier is called a stage and stages used successively are said to be in cascade Sometimes the term is used interchangeably with Daisy Chain Cat 5 Abbreviation for Category 5 catastrophic failure The complete loss of a device s ability to perform its required function Most commonly describes failures that are sudden or involve rapid deterioration Page 54 Category 5 A standard for communications cabling Cat 5 cables are comprised of four pair of twisted conductors a total of 8 wires These terminate in a particular pattern in an RJ45 modular plug Normally Cat 5 cables are used in Ethernet networks and provide a bandwidth of up to 100 MHz at distances up to 100 meters 328 feet There are many variations including enhanced Cat 5 cable with bandwidths of 200 MHz or higher though to achieve high bandwidths all connections connectors cables and devices must be installed correctly carefully tested and certified to operate as advertised Bandwidth and distance are just two of many parameters that must be checked and certi fied for proper performance others include attenu ation crosstalk near end crosstalk attenuation to crosstalk ratio delay delay skew and ultimately even equal level far end crosstalk powersum and return loss Simple LED go no go testers are not adequate to certify cable performance C
99. higher power or signal level amplitude The magnitude of variation in a chang ing quantity from its zero value The word requires modification as with adjectives such as peak maximum rms to designate the specific amplitude in question analog A signal which is continuously variable and unlike a digital signal does not have discrete levels A slide rule is analog in function ANSI An acronym for American National Stan dards Institute Inc Operates a voluntary certifica tion program ASCII An acronym for American Standard Code for Information Interchange Pronounced ass key A 7 bit code used to represent 128 unique letters numbers and special characters An eighth bit is used for parity ASP A filled direct burial telephone cable used in areas subject to rodent attack It consists of a filled cable core corrugated aluminum shield cor rugated steel tape flooding compound and polyeth ylene jacket ASP An acronym for Application Service Pro vider Something like an ISP internet Service Pro vider but instead the ASP sells end users the tem porary access to computer programs via an internet connection instead of using purchased licensed pro grams residing on the users local servers or work stations AT Refers to the IBM PC AT an early personal computer The keyboard connector on this machine was a large round 5 pin DIN connector Subse quent PCs used the same AT Style keyboard
100. ht allow a breach of security to remain inside a locked cabinet inside a locked data center Page 3 Why You Should Be Using These Products Keyboard Video Mouse Switches KVMS solve problems for facilities managers LAN WAN administrators developers of hardware and soft ware and for anyone who wishes to control mul tiple platforms with a single monitor and keyboard Some switch models now are built to address multi ple RS 232 controlled devices including mini com puters mainframes intelligent hubs routers tele phone key systems and voice mail systems from a single dumb terminal or from a telnet interface Some KVMS systems let you mix conventional keyboards monitors mice and terminal emulation to address a mix of RS 232 and keyboard video mouse frame buffered or graphics adapter controlled devices Let s examine some of the benefits Facilities Managers Can Save Space and Power and Improve Work Flow KVMS lets you put a lot more computers in a given space or to use much less space for a set number of computers In one lab for instance IBM Corporation installed KVMS and went from 39 000 square feet to 13 000 square feet a reduction of 67 in required floor space Imagine what you could do with that kind of space savings You can slash floor space requirements even more dra matically by combining special computer racking systems with KVMS Lab Prior to KVS installation Lab After KVS installation 195 ft
101. i console systems today s multi console switches include at least the option for administrator assigned password controlled access for each console port Depending on the user s profile login may allow access to an isolated group of computer systems or to all com puter systems It may allow full control of these com puters video only or video and keyboard mouse but no power on off control on those few KVM systems optionally equipped to cycle CPU power Access control may be implemented by means of on board security within the KVM system or it may rely on the security rights from an existing NT server The handful of recent switches that do rely on NT security represent the first switches in the industry to involve software based control as contrasted to firmware based control The current minimum software related integration includes sys tem administration and event logging of user activ ity on an otherwise hardware based KVM switch Other systems now use software for logging in and actual implementation of switching functions These products probably represent the tip of the iceberg as new implementations are certain to expand the overall functionality of KVM switch systems Consider this if you are in a position to specify the preferred KVM technology for your company you Il need to identify and survey several variables that affect your Information Technology operations A small operation or group may greatly benefit from a
102. ibute electronically or otherwise any part of this document for any purpose without our express written permission except the use of excerpts for critical review by the Press which we welcome In short use for your own reading but don t make multiple copies The authors have spent months and months of valuable time creating this document and we d like to profit fairly from our efforts Page 2 What Are KVM Extension Products It is often useful to extend the distance between a computer or a KVM switch and the monitor keyboard and mouse to which it is connected Ordinary extension cable will work reliable to 10 or 15 feet Higher quality video cables can work as far as 50 or 100 feet if the resolution requirements are not extreme but keyboard and mouse extension just won t flow through a cable at that distance Technical issues of signal timing and level cause errors or just plain failure to function at all Typically video quality does decline with a given unit as the cable length increases up to the point where video and or keyboard mouse response becomes unusable However at a given distance within the supported range whether 100 feet or 500 feet or 1000 feet different products yield very different results Also some KVM extenders do a better job with mouse or keyboard emulation than do others and the results can vary with spe cific computer or KVM switch interfaces As 1s This is not exactly what w
103. idation solid state The use of semiconductor materials in place of vacuum tubes to perform the functions of step index A fiber construction where the core is one distinct index of refraction and the cladding a lower one causing the light to travel down a fiber by reflecting off the core cladding interface strain relief clamp A device used to give mechanical support for the contacts from the weight of a wire bundle or cable strip To remove insulation from a wire or cable SUN A manufacturer of powerful workstations and servers as well as a developer of operating systems and other software for their own and other companies computers superhigh frequency shf A Federal Communi cations Commission designation for the band from 3 000 to 30 000 MHz in the radio spectrum surface mount device An electronic component ranging from discrete passive components to VLSI chips attached to the surface of a printed circuit board either directly or through a surface mount connector rather than by means of holes in the board surge A transient variation in the current and or potential at a point in the circuit SVGA Super VGA see VGA A higher resolu tion version of VGA video that is typically 1024 horizontal by 768 vertical pixels but may refer to higher resolutions of 1280 H x 1024V or even 1600 H x 1200 V pixels though the latter may also be known as XGA swedging Another term for crimping swit
104. ily damage the monitor s or video card s circuitry analog signals peak at 0 7 to 1 volt not 5 volts like TTL digital Analog cards typically use HDD 15 15 pin D connector with 3 rows of pins outputs Not all 15 pins are used for signals but in XGA II video some of these pins are used to convey coded information about the monitor back to the video card Macintosh Video Past and Present The Macintosh series of computers from Apple have evolved along a different path than PCs but there are many similarities Early Macs from 1984 to about 1987 had built in monochrome video the Mac Mac 512 Mac Plus and Mac SE First via third party adapters and subsequently through Page 9 Apple s own designs as well plug in video adapt ers made it possible to use larger external moni tors color gray scale or monochrome The Mac SE and all subsequent Mac II and Power PC Macs have incorporated this capability although the newer iMac is the first DB 15 Connector Used for recent Mac to rely pri Early Macintosh Video marily on a built in video display Depending on the third party vendor the inter face between the adapter card and the monitor will vary DB 15 and HDD 15 are most common but some video card and Mac monitors made use of sin gle or multiple BNC coax connectors Apple also supplied built in video circuitry on the mother board with external video output on a number of platforms including the Mac I
105. ing devices to most efficiently utilize the product s features Our technically oriented people are familiar with the LAN administrator s responsibilities If you have an application that you feel involves an unavailable as yet undeveloped product we sug gest discussing the application with the authors of this paper they may know whether a particular vendor has a suitable new product or one in devel opment On more than one occasion customer con sultations and the field engineering efforts of our firms have resulted in manufacturers creating new or modified products to meet the newly identified need If you have initially had a negative impression of the whole concept of KVMS you are not alone Be aware though that many delighted users of KVMS were initially skeptical The authors have expended substantial efforts to be comprehensive accurate and unbiased in the rep resentations within this document If you are aware of a specific inaccuracy or a significant omission please contact the authors valid and pertinent input will be welcome and will find its way quickly into a revised document Tron International and The WorkCenter employ special technique s to design KVM Switch Systems into KVM Networks We help you configure an array of products to meet the special needs of a broad spectrum of users each product designed to represent equality in the actual deployment of throughput and user accessibility If y
106. interfaces Some video driver cards are now being made to drive digital ready CRT cathode ray tube 1 e conventional monitors not necessarily USB standard as well With modern high speed low cost digital circuitry it has become possible to get more accurate high resolution images by keeping signals in the digital domain rather than converting them to analog or 1f analog conversion is done it occurs right inside the monitor Analog Video for PCs Further along in PC development manufacturers began to use analog signals to convey video from the display adapter card to the monitor Here the video intensity is defined by a continuously variable voltage that typically ranges from zero to 700 mil livolts mV DC per color The monitor includes circuitry to map these signals onto the screen and amplifiers that deliver the appropriate intensity Analog based video encompasses VGA Versatile Graphics Array SVGA Super VGA and XGA Extended Graphics Array cards among others Today s analog cards typically have much higher resolution more pixels displayed than older TTL cards Technical details may not matter to you but this does you cannot directly connect a TTL video card output to a VGA monitor or vice versa First of all the cables do not mate but if you were to some how wire up an adapter you would fail to see the HDD 15 Connector Used for correct image and you Analog VGA SVGA Video could eas
107. introduced to PCs via plug in circuit cards This third party approach resulted in three different types of PC mice the bus mouse the serial mouse and the PS 2 mouse Bus mice are seldom seen today The Serial mouse was popularized by Microsoft and uses a DB 9 connector just like that of a TTL video circuit but the connector s sex avoids any chance of misplugging The PS 2 mouse introduced by IBM and now adopted by most PC vendors uses a mini DIN 6 connector just like the PS 2 keyboard Each PC s operating system O S must be equipped with the appropriate driver soft ware to match the type of mouse in use If you use a simple adapter to hook up a true PS 2 mouse to a PC with a serial mouse port it won t work properly In fact serial mice use more wire leads than PS 2 mice A special class of combo mouse labeled Serial PS 2 can work in either serial or PS 2 mode as determined by sensing the PC hardware to which it is connected refer to the mouse dis cussion in Product Function For The Technically Oriented Reader These mice have a female DB 9 serial connector and an adapter which converts this to PS 2 An ordinary PS 2 mouse will not work with a serial adapter Most PC mice or trackballs have two or three buttons Mac mice and trackballs generally have one button though some have additional special function buttons the Mac O S does not recognize a right mouse click as does Windows Windows N
108. ional power supply in designs where they are not always needed Power PC Refers to an Apple Macintosh or other computer as some IBM RS 6000 s using a Motorola RISC based CPU such as the 600 series 603 603e 604 604e or later on the G3 or G4 CPU printed circuit A conductive pattern that may or may not include printed components formed in a predetermined design on the surface of an insulating base in an accurately repeatable manner The two most common types of printed circuits are etched and plated printed circuit board A plastic epoxy or similar board substrate to at least one layer of printed circuitry is applied The board is usually drilled for component mounting with or without printed com ponents and typically is then fitted with separately manufactured parts that are manually or machine soldered in place Page 68 printed circuit edge connector A connector designed specifically for making removable and reliable interconnections between the terminal area edge pads of a printed circuit board and the exter nal wiring printed element An element in printed form such as a printed inductor resistor capacitor or trans mission line Printed elements can be formed on printed circuit boards along with connections Also called printed components printed wiring A type of printed circuit intended primarily to provide point to point electric connec tions and shielding Often this is in the form of a
109. isplayed at a resolution of 640 H nor EGA is impressive x 350 V pixels S you can view 9 page 11 x 17 inch to view a 2 SVGA Uniform Resolution Map slightly reduced image size out to the page edges Today these large monitor at SVGA Uniform Resolution Map users with fine lines and well formed type allowing them to work long hours on complex images with 9 less visual fatigue The 1024 H x 768 V pixel dis play on a 19 to 21 inch diagonal monitor affords Both modes provided graphic designers and CAD page layout at full size WYSIWYG What You See Is What You Get minus about a half inch the opportunity border and you just don t find it in recently designed computer equipment 9 stay with TTL video Graphics using analog monitor technol is capable of displaying up to 256 colors simul taneously with a resolution of 640 H x 480 V pixels VGA preserves about the same aspect ratio as EGA 9 EGA Uniform Resolution Map Because TTL video uses modest amounts of RAM random access memory a few servers were standard in 1987 when it rolled out the VGA Uniform Resolution Map IBM introduced the VGA Versatile colors the smaller the steps For example 256 color a zero to 700 mV signal in discrete steps the more equipped with these cards long after VGA became the norm elsewhere Today RAM is so inexpensive but with 16 times the number of colors VGA uses that there is no
110. l at a time For example all bits of an 8 bit word are transmitted one bit at a time over a single line serial transfer Data transfer in which elements of information are transferred sequentially series circuit Connecting components in a cir cuit end to end to provide a single path for current flow series topology A computer or switch network layout in which the various components are linked one to the next Also known as a daisy chain server a computer which hosts holds a database application program or other files and makes them available for access by other computers the cli ents typically via a Local Area Network LAN connection server farm A collection of servers in one physi cal area typically in a data center SGI Silicon Graphics Incorporated a maker of specialized computers and software often used for high resolution graphics map making film video special effects and animation Sheath The outer covering or jacket over the insulated conductors to provide mechanical protec tion for the conductors Also known as the external conducting surface of a shielded transmission line Shell An encapsulation for inserts or modules Mating shells usually provide proper alignment and protection for the contacts enclosed in the inserts or modules shf See superhigh frequency shield shielding A conducting envelope com posed of metal strands that encloses a wire group
111. llows a light signal to take various paths to arrive at the end of the fiber causing some light rays to arrive later than others do multiplex The simultaneous transmission of two or more signals using a common carrier wave or a single path in a transmission system Early exam ples would include the transmission of stereophonic fm broadcasts and the conveyance of multiple voic es over a single telephone line In KVM switching and extension products often a single pair of con ductors conveys keyboard mouse and sometimes even audio data by means of multiplexing these various signals N NAB Abbreviation for National Association of Broadcasters For several years prior to January 1 1958 it was known as National Association of Radio and Television Broadcasters NARTB nano A prefix meaning 109 which is 0 000000001 or one billionth nanosecond One billionth of a second NEC Abbreviation for National Electric Code Also Nippon Electric Company NEMA Abbreviation for National Electrical Man ufacturers Association node 1 An electrical zero point Specifically a current node is a point of zero current a voltage node is a point of zero voltage 2 An end point to any branch of a network or a junction common to two or more branches Terminals and other equip ment that communicate over the network are nodes in a network noise An extraneous signal in an electrical circuit capable of interfering with t
112. mands and or a menu system some times known as OSD for On Screen Display OSG for On Screen Graphics or a similar acronym While the active KVMS has traditionally cost more than the passive KVMS the difference has nar rowed with the introduction of reasonably designed inexpensive active switches from a number of man ufacturers In almost every case active switches are the superior solution so we do not go into much detail about passive switches in this document We ll use the word mouse or mice loose ly to mean any cursor controlling device which includes trackballs trackpads joysticks and so forth Just remember that in a given instance not all such devices may actually be usable With few exceptions the operating system soft ware and or the BIOS basic input output system of the PC checks for the presence of a connected key board when you first power up boot the computer if no keyboard is connected you see an error mes sage on the monitor and the system does not start up properly For this reason most passive KVMS switched computers can be booted only when they have been selected on the switch After a system shutdown it will take a long time to start up each computer because someone has to manually switch to each computer turn it on etc Today s active keyboard video switches emulate the presence of a keyboard and mouse to all con nected CPUs This means that you can turn on all the comp
113. monitor more typical of a television set frame or refresh rate is half the vertical sync frequency For example 70 Hz interlaced paints a new screen 35 times per second The non inter laced video requires significantly higher bandwidth Anything above 75 Hz for the monitor s prime reso lution setting is considered VESA standard a rat ing system that enables a monitor vendor to use the flicker free logo The refresh rates decline at higher resolutions because the number of pixels the monitor must refresh increases slowing down the refresh speed The horizontal sync frequency is measured in kiloHertz kHz or thousands of Hertz It is derived by multiplying the vertical sync frequency refresh rate in non interlaced mode or 2 x refresh rate in interlaced mode by the number of horizontal lines In other words the sync frequency also increases with greater numbers of pixels displayed The typi cal horizontal sync frequency for a 14 inch VGA monitor is about 31 5 kHz though very high resolu tion monitors can have sync frequencies upwards of 100 kHz The video bandwidth however is about 28 MHz on the 14 inch monitor Video bandwidth is calculated using the sync frequency interlace and the number of pixels dis played as well as the blanking interval or dead space between images Video bandwidth is equal to H pixels x V pixels Interlace factor x Vertical sync rate For typical VGA uncorrected Video Bandwid
114. mputing environment Using the KVMS is a lot easier but you re reading this section because you want to know more than the average user Color Depth A monochrome monitor is a not a bit display the screen can be off on or high intensity for a given pixel When the electron beam in the CRT cathode ray tube turns on the phosphor color of a typical monochrome display will be white green or amber One variation is the gray scale monitor Gray scale monitors use 2 4 or 8 bits of data to define 4 64 or 256 levels of intensity for each monochrome pixel not just on off Typical 0 28 mm dot pitch CRTactually has different horizontal and vertical pitch All Color Monitors Use Red Green and Blue Phosphors Higher Resolution Models Have Smaller Dots That Are Spaced More Closely AND They Have Electronics To Handle Higher Bandwidth Signals Today you may find color displays that use 4 bit 8 bit 16 bit or 24 bit data words to define respectively 16 256 32 000 or 16 7 million colors 32 bit color display cards are available but they actually use 24 bits to define the displayed color and the remaining 8 bits for other functions over lays transparency cut paste channels etc Color monitors utilize three different phosphor dots red green and blue to define a single pixel Each phos phor can be illuminated to varying degrees of inten sity depending on the available color depth of the display card driving the monitor
115. multi user access so their costs may be significantly higher We suggest that you add up the cost of the switch plus cables and necessary accessories power supplies remote controls mounting hard ware Then subtract the cost of all the monitors and keyboards and mice and racking you won t need and divide this by the number of computers being switched If the result is a positive number you get an idea of the direct switch cost per switched computer Negative numbers indicate how much you ll save per switched computer Of course you will have indirect savings too such as reduced floor space requirements better personnel efficien cy don t under estimate this factor lower power usage and lower HVAC air conditioning costs Cables Since the first edition of this White Paper in 1995 cable pricing has become more competitive In addition to KVMS that use specialized cable sets these still make sense due to their locking con nections many KVMS models now use standard separate keyboard video and mouse cables These have brought down cabling costs in some instances Some manufacturers still require you to daisy chain connections from one computer to the next on the way to the switch this may save in overall cable length but it makes things more complex if you want freedom in layout of individual computers And as stated previously not all cables are of equivalent quality cables with controlled imped ance
116. n it upgraded from version 3 51 to 4 x and reports have come in that some switches don t work well with Linux In reality in many cases the O S does matter and compatibility is a function of how well the emu lation is implemented The KVMS must return the correct keyboard and mouse codes to the connected computers For example KVMSs that don t under stand about different scan sets inside the IBM 101 keyboard will have problems To the extent that the O S affects the code interchange the KVMS must be set up to interact properly with the O S Intelligence in the KVMS handles this interac tion and the intelligence is generally coded in firm ware If the firmware does not match the mouse or keyboard drivers in the O S software control can be erratic You may have lags in mouse response delayed keyboard response constant mouse button locked down mode or a complete failure to func tion Sometimes it just takes a software update to a current driver or version of the O S or a firmware update on the KVMS to fix the problem Sometimes what appears to be an O S compati bility issue turns out to be an indirectly related driv er issue There may be certain video or mouse driv ers for example that are configured and selected along with the operating system When you install or select a different O S and encounter problems you may inadvertently have selected these different drivers For example if the video driver changes f
117. nd Timbuktu allow one computer to be viewed and controlled from another by means of in band communication if the computer being accessed is locked up or hung the access is not usable Conversely out of band remote access control solutions directly address the keyboard video and mouse ports inductance An electromagnetic phenomenon in which the expanding and collapsing of a magnetic field surrounding a conductor or device tends to impede changes in current The effects of induc tance become greater as frequencies increase The basic unit of measurement for inductance is the henry Inductance can be a component of reactance inductive coupling The coupling of energy from one circuit to another that results from the magnetic field generated by the source conductor inductor A circuit component designed so that inductance is its most important property Also called a coil insertion loss The loss in load power due to the insertion of a component connector or device at some point in a transmission system Generally expressed as the ratio in decibels of the power received at the load before insertion of the appara tus to the power received at the load after insertion insulation A material having high electric resis tance making it suitable for covering components terminals and wires to prevent the possible future contact of adjacent conductors resulting in a short circuit integrated circuit IC
118. nd low power consumption coaxial cable A transmission line consisting of two conductors concentric with and insulated from each other In its flexible form it consists of either a solid or stranded center conductor surrounded by a dielectric A braid is then woven or swerved over the dielectric to form an outer conductor and a waterproof plastic covering normally vinyl is placed on top of the braid The degree of flexibility in coaxial cables is indicated by the terms flexible semi rigid or rigid coaxial ribbon cable Ribbon cable consisting of parallel coaxial conductors joined together in a flex ible insulating material and designed for mass ter mination color coding The selective placement of color on a terminal or contact to aid in its identification and to assure proper selection of the correct wire size and crimping tool color depth Refers to the number of bits of infor mation used to encode the color of a given pixel on the screen bit is monochrome on off Typi cally gray scale monitors use 2 4 or 8 bit color depths to represent 4 64 or 256 phosphor intensities respectively in just one color Color monitors use 4 8 16 or 24 bit color depths to represent 16 256 32 000 or 16 7 million colors respectively common mode EMI Interference that appears between both signal leads and common reference plane ground and causes the potential of both sides of the transmission path to be changed simul
119. nly for the dura tion of the transmission of the packet Computer networks often transfer data by means of packet switching parallel circuit A circuit in which two or more loads are connected to a single voltage source at a common point or along a common bus parallel operation In computers the simultaneous transmission of data on separate lines For example all bits of an 8 bit word are sent simultaneously on eight separate lines Parallel operation can be much faster than serial operation but requires more circuitry and more complex cabling Recent very high speed serial circuits outperform many parallel circuits parity A method by which binary numbers can be checked for accuracy An extra bit called a parity bit is added to numbers in systems using parity If even parity is used the sum of all 1 s in a number and its parity bit is always even If odd parity is used the sum of s in a number and its parity bit is always odd Parity is one of the parameters which must be set when establishing a modem com munication or setting up a serial data terminal parity bit A binary digit appended to an array of bits to make the sum of all the bits always odd or always even parity check A technique for detecting errors It consists of summing the l s in a specific length of data and recording whether the sum was odd or even in a parity bit line A single error would change the sum and thus be detected Stated ano
120. nnectors DIN 5 are used for older AT style keyboards whereas mini DIN 6 are used for PS 2 type keyboards and mice and mini DIN 8 are used for Sun keyboards diode A two terminal single junction semicon ductor a rectifier which exhibits different con duction characteristics depending on the polarity of applied voltage A forward biased conventional p n diode has a low impedance Reversing the polarity results in a reverse bias diode and a high imped ance A diode normally passes current in one direc tion only Some diodes emit light and are known as LEDs see light emitting diodes DIP Abbreviation for dual in line package distortion An unwanted change or addition to a signal or waveform when it is amplified This definition excludes noise which is an extraneous signal superimposed on the desired signal distributed element filter A filter whose filtering properties such as capacitance and inductance are distributed uniformly along the length of the filter driver 1 Small programs that control external devices or execute other programs 2 The amplifier stage preceding the output stage in a KVM switch extender transmitter or other device 3 The portion of a particular type of loudspeaker that converts electrical energy into acoustic energy and feeds it to the small end of a horn this 1s actually a compres sion driver Page 59 dual in line package DIP A family of rectan gular integrated circuit
121. not be dis cussed in the manufacturer s advertising It is also worth considering whether and how the firmware can be upgraded for the switch Changes in operating systems and computer architecture have over the years repeatedly rendered the firm ware on various switches to be less than ideal and in some cases have made the switch unusable The ability to upgrade firmware should be considered essential since a relatively minor cost or free firmware upgrade can preserve a large investment in switch hardware and installation On the other hand you would like to have firmware be reason ably stable before it ships Some manufacturers have released tens to dozens of firmware revisions in the same time that other manufacturers have remained current with just a few releases how often do you want to HAVE to upgrade firmware Page 35 Multi Console KVMS Systems The New Standard The Explosion in Multi Console Switching System Architectures The multi console KVMS system architecture you choose will impact the infrastructure of your data center in ways you might not expect These systems come in a wide range of styles with dif ferent feature sets physical sizes unit and overall capacities and cabling requirements Each different KVMS topology requires various components that affect everything from rack space vertical RU s within individual racks to the data center s AC and KVMS chassis interconnect wiring In some KVMS
122. o be connected to it with internal circuitry to convert control protocol from a given mouse to properly drive a variety of connected computers which may be using different mouse drivers Some KVMS systems employ one microproces sor for the keyboard and another for the mouse while some use a single microprocessor for both functions Its interesting to note that the 8042 key board controller used in today s computers is the same chip used in early PCs This chip is a dual channel device and the second channel can be used for control of the mouse Each approach has its pros and cons Dual microprocessors can create problems if the micro processors do not switch in perfect synchronization as the user selects various computers KVMSs with a single microprocessor for both keyboard and mouse may rely upon that microprocessor to control multiple switching channels 1 e four to eight com puters This avoids synchronization problems but may cause delays if the microprocessor cannot keep up with the demands of the multiple mouse and keyboard emulated ports Several manufacturers now use a single microprocessor per channel per switched computer in an effort to avert synchro nization and throughput problems This approach tends to be more expensive and is therefore found in switches costing a bit more The point is not all switches are created equally and you need to evalu ate how their design will affect their performance in your ap
123. of Video for Computers some operating systems and com puter systems draw windows based on the available screen real estate and thus they must know the pixel map capability as well as in many cases the color depth and refresh rate of the connected monitor Apple Macintosh Sun Sparc and some Silicon Graphics platforms as well as certain IBM RS 6000 and XGA video platforms require video sense feedback VESA a standard for video pub lishes a DDC specification for defining monitor characteristics and communicating this between monitor and computer KVM switches built to sup port platforms that require video sense data must be able to be automatically or manually set to convey this data to attached computers in such a way that the monitor s used can display the incoming video signals Today a manufacturer of KVM switching or extension products can purchase chips that perform keyboard and mouse emulation Chips or circuit cards are available to perform terminal emulation Yet inclusion of these off the shelf products in a KVMS system is no guarantee of broad scale emulation Because operating systems are regularly updated and computer hardware undergoes regular cycles of innovation and change so too must KVMS products be regularly updated In most cases 1t is the firmware not the switch hardware that will fail in the face of change You may experi ence this as a hung or erratic mouse a locked up or inappropriate keyboard respons
124. of wires or cable so constructed that substantially every point on the surface of the underlying insula tion is at ground potential or at some predetermined potential with respect to ground An isolation barrier placed around a circuit compo nent to prevent interaction of its electric and or magnetic fields with those of nearby elements signal to noise ratio The ratio of signal strength to noise level in an electronic system significant digit A digit that contributes to the preciseness of a number The number of significant digits is counted beginning with the digit contrib uting the most value called the most significant digit and ending with the one contributing the least value called the least significant digit silicon The semiconductor material most widely used for transistors diodes and monolithic inte grated circuits A brittle gray light metal silicon controlled rectifier SCR A semicon ductor device capable of only two stable states When off it blocks the flow of electricity in either direction A small triggering voltage to its gate turns it on and allows the flow of electricity in the forward direction only When on the SCR acts just like a conventional rectifier To turn it off voltage to the anode must be removed or reduced to a potential less than that being applied to the cathode simplex A circuit which allows telecommunica tions in only one direction at a time
125. oint links in an unbroken circular configuration RISC Acronym for Reduced Instruction Set Com puter a type of computer CPU that has a smaller internal set of programming instructions than CISC complex instruction set computer but which runs faster because of it and provides generally faster overall computational power than CISC computers The IBM RS 6000 series and Apple Macintosh Power PC series among others utilize RISC CPUs rms See root mean square ROM Read only memory A memory usually a semiconductor chip in which the information is permanently stored ROMs offer random access read capabilities May be programmed during man ufacture or by the user Some are reprogrammable See PROM and EPROM root mean square The effective value of an alternating current corresponding to the direct cur rent value that will produce the same heating effect Page 71 rotary switch A multiposition switch operated by rotating a control knob attached to its shaft either clockwise counterclockwise or both RS 232 422 449 A series of standards defining the physical link between units of data communica tion equipment The most common serial interface is probably RS 232 RU Rack Unit An EJA standard for vertical mea surement in a telecommunications or computer rack or cabinet One RU equals 1 75 inches two RU is 3 5 inches and so forth Due to the additional space needed for framing a cabinet may b
126. olor Depth Specifications is Not All Inclusive NTSC Video is Not Optimum for Computers NTSC National Television Standards Committee video is analog as is VGA but that s about the only similarity The frame rate is Just under 30 Hz that is there are about 30 full images per second being displayed However because each TV style image is drawn by two sequential scans of the screen one beginning in a corner of the screen and the other beginning in the middle of the screen the effective refresh rate per scan is about 60 Hz see the illustration of interlaced vs non interlaced video scans Phosphor persistence the amount of time it glows after being hit by the elec tron gun plus human perception merges the two low resolution scans into a single higher resolution full screen image This kind of TV display is known as interlaced video Interlaced fields are intended to reduce video bandwidth but because an entire screen 1s produced at half the Vertical Sync rate this causes flicker Interlacing in itself does not cause reduced sharpness but the monitors that rely on interlacing to get higher resolution are usually cheaper and inherently less sharp than more expen sive non interlaced monitors Computer video is increasingly non interlaced interlaced technology is dying despite a large installed base non interlaced means each scan is a whole frame that sweeps the entire screen with the entire video image not two fields
127. ons and AT keyboard connectors The reason for this 1s that the PS 2 mouse is capable of the 2 way communication that the PS 2 comput er s mouse port requires but will also fall back to 1 way communication when translated to serial pro tocol The inverse is not possible PS2 Serial Mouse Adaptor is Only Usable With Special Combo Mice Many Adaptors Work Differently Microsoft Intellimouse Beside Logitech s Wireless Wheel Mouse left A newer variation of the PS 2 mouse is the Wheel Mouse Whereas a traditional PS 2 mouse uses 3 byte data packets of 8 bits per byte the newer wheel mice use 4 or 5 byte data packets Microsoft s Intellimouse uses 4 byte coding and some of Logitec s Wheel Mice use 5 byte coding with the extra byte used for a proprietary extension to support a third mouse button Not all KVM manufacturers have changed their firmware to sup port these newer mouse protocols In addition to the protocol changes the wheel mice use different wir ing within the cables so that while the connectors appear to be the same they don t necessarily work the same Trackballs while they perform the same func tion as mice sometimes use proprietary drivers which are not necessarily supported by a given model of switch USB Connections The Universal Serial bus is relatively new It is a medium speed serial bus that permits connection of a large number of external devices to a computer with hot plug on t
128. onsole Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console L Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse System Chassis Hybrid Figure C Here the Series Star and Expanded Star Architectures are All Utilized in a Single KVMS System The larger the KVMS system the more com plicated it gets KVMS systems that utilize the Expanded Star and Hybrid models are configured with user and system chassis but also include a middle section for KVM signal routing Think of the middle section as a router or hub though it does not handle IP or data at all it may or may not support direct connection of additional local computers There are three distinct approaches to how the hardware is designed in the Hybrid model In all of these inexpensive category 5 cable usually is the interconnecting medium The hardware located near the computer will include simple extension technol ogy to compress and transmit KVM signals over the Cat 5 The manufacturer s design determines whether or not switching is actually performed near the computers Some KVMS systems transmit the signal to a central hardware piece where the distri bution matrix is ac
129. or emergency access in the event of a failure in any component that affects more than one CPU In general the most common source of failures in electronic devices is the power supply so it is important to have a reliable supply Not only can the loss of power immediately cause all opera tion to cease the power supply itself generates heat which if transferred to nearby electronic circuits can shorten component life Some manufacturers try to reduce heat concerns by using external power supplies Power bricks that are large enough to power a multi port KVMS can fall out of an outlet making them a potential weak point so secure external supplies carefully if you use this type A few manufacturers of KVMSs have models that use the same power that would have powered the keyboard on a given computer to power the cor responding circuitry in the KVMS with one such external power supply computer per port such KVMS have a distributed power supply so no sin gle failure will bring down the entire KVMS and there is no power supply inside to generate heat However if the KVMS draws too much power from a computer it can blow an internal fuse on the computer typically a motherboard mounted Page 47 pico fuse while this can be replaced it is incon venient so you will want to be sure that the com puter can support the power drain of such a switch The largest multi user KVMS systems today have field installable hot swap c
130. other side of the equation the Compaq ProLiant 7000 senses keyboard current draw during boot up something no prior computer has done our knowledge a KVMS that doesn t have the correct keyboard input impedance may cause boot errors on this particular computer A few KVMS systems use the keyboard power output of the CPU only for emergency emulation services in the event of a KVMS power supply failure It can be beneficial if the KVMS stores key scan codes and mouse type information about each PC in non volatile memory Should power to the switch be interrupted you would not then have to reboot each CPU in order to restore proper switch opera tion Absent this feature you may want to put the KVMS on a UPS Uninterruptible Power Supply In fact a UPS for the KVMS is a good idea for the simple reason that UPS power will eventually run out unless there is a backup generator and if you must shut down the CPUs before the UPS batteries expire you ll want to have the KVMS working so you can issue the shut down commands As mentioned previously in this document SGI Silicon Graphics has employed a several differ ent keyboard mouse stan dards Their 4D series Indigo Crimson and Onyx systems use an up down encoded 101 key keyboard with a bidirec tional serial link Every key has an upcode and downcode and the key board itself has connec Some SGI Keyboards Use DB 9 Some Use Non Standard PS 2 and Others tors on bot
131. ou would like information on a specific product or consultation regarding a particular appli cation please contact tron com Tron International Inc PO Box 25596 San Mateo CA 94402 5596 650 525 2700 Tel 650 525 2707 Fax 800 808 4672 Toll Free Info tron com www tron com The WorkCenter Corporation The WorkCenter Corporation 1206 Appleton Way Los Angeles CA 90066 310 737 7530 Tel 310 737 7531 Fax 800 526 6625 Toll Free Sales The WorkCenterCorp com www TheWorkCenterCorp com V2 0 1a
132. plication History of the Mouse The Mouse has evolved from a research device at the Xerox PARC facility in Palo Alto CA in the 1970s to a commercial product of very limited distribution in Xerox STAR word processing page layout system around 1979 or 1980 then to wider use in Apple s Lisa and its successor the Macintosh Later and of course it later became a standard in the earliest versions of Microsoft Windows In a manner that would have pleased Charles Darwin the mouse has evolved ever since its incep tion It is not our purpose in this document to detail obsolete devices One of these while it still exists is the Bus Mouse which was an early implementa tion for PCs The bus mouse had only motion sens ing built in and it relied on an ISA card in the computer to interpreted that motion Connection was via a 9 pin Hosiden connector not the DB 9 connector used in subsequent Serial mice While a few Bus Mice may still be in use only one KVM switch manufacturer sup ports the Bus Mouse so we re not going to discuss this now obscure technol ogy any further The Serial Mouse came next and is still common It relies on active electronics that internally code mouse motion and communicates it to the CPU via a serial protocol to a serial port The Serial Mouse uses DTR and RTS lines to bring 5V power into the mouse for powering its microprocessor The original serial pro tocol supported two action buttons Logitech
133. popular bipolar logic family based on a multiple emitter transistor Compared to MOS logic TTL is gener ally faster although it uses more power and offers less packaging density Older computer video dis play technology such as MDA CGA and EGA used a digital signal based on TTL compatible voltage levels U uhf See ultra high frequency UL Underwriters Laboratories Inc An indepen dent laboratory that tests equipment to determine whether it meets certain safety standards when properly used UL does not certify equipment they merely list it as being compliant if it meets the particular standard for which it is listed ultrahigh frequency uhf A Federal Communi cations Commission designation for the band from 300 to 3000 MHz on the radio spectrum In televi sion channels 14 to 83 or 470 to 890 MHz ultrasonic welding Process using vibratory mechanical pressure at ultrasonic frequencies 20 to 40 kHz to provide heat for welding some types of thermoplastics Page 75 uniform resolution map a term we invented to describe a printed graphic representation of the number of horizontal and vertical pixels on a dis played image This is not actually the number of lines or dots but merely a way to show the relative density of dots on a given image when comparing various resolutions An aid to visualization only UNIX A popular operating system originally developed by Bell Labs Today Unix and its vari ants
134. puter system and of the switch or extension system being considered SGI keyboards also vary as described in our detailed technical section NTSC Video In the United States of America broadcast television has relied for decades on a video standard defined by the NTSC National Television Standards Committee NTSC standard video is an analog signal TV sets cannot generally be con nected directly to computers due to a number of dif ferences in the way they define the video signal In the technical section of this document we discuss some of these differences including interlaced vs non interlaced video frames and other modulation differences Keyboards Mice Wheel Mice Trackballs Trackpads Today s workstation and server keyboards all have roughly the same set of alphabet punctuation and numeric keys Keyboards generally have 85 or 101 keys though there are many exceptions In any case you will not find 85 or 101 wires coming out of the keyboard typically just 5 or 6 wires because keyboards include a microprocessor that scans the keys to determine which are being held down and then codes that information into signals which can be defined by an 8 bit serial data stream With a few exceptions most computers use ASCII definitions inside their circuits ASCII is an acronym for American Standard Code for Information Interchange pronounced ass key Keyboards however use a concept called scan co
135. r optimum conditions though requires more memory which may not be avail with the ideally specified cabling manufacturers able In the case of video manufacturers generally state limitations based on a more conservative view specify the number of hops a KVMS system can of how their products will be used Additional effectively achieve without deterioration of the single console KVM switches may be used to video signal In some applications where the opti extend these products beyond the stated chassis System System Chassis Chassis Multi Console Multi Console Keyboard Video Mouse Keyboard Video Mouse System Chassis System Chassis System Chassis and or KVM Hubs Multi Console Multi Console Multi Console Keyboard Video Mouse Keyboard Video Mouse Keyboard Video Mouse User Router Chassis System Chassis System Chassis Chassis Multi Console Keyboard Video Mouse Multi Console Multi Console User Chassis Keyboard Video Mouse Keyboard Video Mouse 1 Router Chassis Vinee System Chassis Keyboard Video Mouse System Chassis Ke S se Mul oneal y i u Multi Console SUE ESE R Keyboard Video Mouse VEUS EIME ESE User Chassis Multi Console Multi Console Keyboard Video Mouse Keyboard Video Mouse System Chassis Multi Console Router Chassis Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse j User Chassis Multi Console Keyboard Video Mouse M COE Router Chassis Multi Console Keyboard Video Mouse Keyboard Video Mouse System Chassi
136. rap Trademark of the Gardner Denver Corp for a wrap type termination word A set of bits constituting the smallest addressable unit of information in a programmable memory word length The number of bits in a word write To deliver data to a medium such as stor age WYSIWYG An acronym for what you see is what you get Refers to the accuracy of an on screen representation on a computer of a printed page both in dimensions and character image shape Typically WYSIWYG resolution requires a pixel density of 72 dots per inch where one dot equals one point though it can be almost WYSI WYG at up to 80 dpi a slightly reduced size image XYZ X Letter symbol used to represent reactance not resistance in ohms reactance is the opposition to the flow of alternating current as contrasted to resistance the opposition to the flow of direct cur rent XGA Extended Graphics Array or Adaptor A higher resolution video card and standard a version of VGA and SVGA typically 1280 horizontal by 1024 vertical pixels XGA video typically makes use of sense lines returning information from the monitor to the computer so the computer knows the size and resolution of the screen image it must render Page 77 XT Refers to the IBM PC XT an early PC Z Letter symbol used to represent impedance in ohms zener diode Normally used to regulate voltage A p n junction diode reverse biased into the break do
137. rations for clarity avoid arbitrary printing form related page limits give you the benefit of hyper text links and update the content more frequently as ongo ing technical developments may warrant If you re reading a printed version it may have been sponsored by one of the industry s leaders under license from the authors or it may have been printed by someone who paid the licensing fee to unlock the PDF file for printing purposes We suggest that you visually scan the pages quickly at first then use the hypertext links to jump to sections that interest you We see many changes in the future KVMS industry This document and it s subsequent revisions will remain a valuable reference be sure to visit the websites Www tron com or www TheWorkCenterCorp com periodically to download the latest version one purchase of the unlocked PDF document validates future version updates if you don t purchase the unlock code you can still access summary information but you won t have the whole story The driving force behind KVMS development was the rapid deployment of local area networks LANS relatively rapidly client server software with microcomputers on each desk replaced the old Mainframe terminal mega application paradigm With LANs came a massive proliferation of servers in the data center lots of boxes and nowhere to put them all The KVMS was a welcome develop ment because it eliminated a lot of those boxes monitor
138. reason to PS 2 family VGA Adapter ogy and high resolutions are commonly used in work a day situations where users wish to display multiple partially overlapping or completely unblocked win dows for one or more applications Some designers multimedia producers and CAD operators required still higher resolution and IBM introduced 8514 A video which had a 1024 H x 768 V resolution in interlaced mode as well as VGA compatibility This approach had flicker problems and has been largely abandoned in favor of the subsequent XGA standard which is capable of color depths to 16 7 million simultaneously dis played hues 1 e virtually continuous display of the full color spectrum without banding and optional resolutions of up to 1280 H x 1024 V pixels Because a given monitor might not be capable of displaying such high resolution images or since high res mode might not be desirable if the screen size were small XGA II video monitors include signal wires that tell the display card about the type of monitor in use so the card can generate appropriate images Even the best conventional 19 to 21 diagonal
139. requencies though there are other aspects to the conversion that may still have to be handled by the KVMS video sense data for example Bandwidth in MegaHertz values compensated for Horiz amp Vert Retrace Page 26 Bandwidth in MHz vs Resolution at Various Refresh Rates H 284 2 non interlaced display Lii N N LL L LAS _ ME o S O BYA K VN JRZ AVI rs d y h wo _ _ 4 es O re WH 250 7 480 600 768 370 1024 1200 1200 ideo Resol mion Hor 7 ert Pixe Page 27 First there was TTL Transistor Transistor Logic The original PC video signal was capable of limited resolution The MDA Monochrome Digital Adapter provided single color display at a reso type against a black background European research lution of 720 H horizontal by 350 V vertical pixels Typically you would see white or green indicated that amber was less fatiguing so soon yellow on black monitors appeared All used the same MDA card just different phosphors in the CRT Monitor Types amp Standards are available to not all KVMS 9 Mac require information about 9 line with traditional Mac video circuitry screen resolution data that returns to Sun the monitor size or resolution and even the Even though resolution data may be returned Aside from different sync frequencies some to the computers by the KVMS In line Package switches These let the user
140. res information temporarily during data transfers Often used to isolate one part of a circuit from another or to facilitate data transmission synchronization burn in Operation of a circuit or equipment to stabilize all components and reduce failure rates bus Originally uninsulated conductor wire bar etc may be solid or hollow round or rectangular Sometimes used to indicate bus bar Conceptually a bus is a major circuit path to which other circuit ele ments apply or from which they derive power sig nals or data One or more primary conductor paths used to transmit information from any of several sources to any of several destinations bus bar A heavy bar or strap usually of copper for carrying heavy currents or serving as a common connection between several circuits Often used in datacomm cabinets or data centers to provide a common electrical ground bus network A network topology in which nodes are all connected to a single line serving as the bus byte A group of eight bits that define a character or data word C cable Either a stranded conductor with or without insulation and other coverings single conductor cable or a combination of solid or stranded con ductors insulated from one another multi conductor cable In fiber optics a jacketed fiber or jacketed bundle in a form which can be terminated cable assembly A completed cable with its associ ated connectors and or hardware cable
141. ribution and throughput with just a few compo Page 40 nents or across several hardware pieces The latter incorporates a higher level of redundancy and will provide protection from component failures regard less of the product brand To properly evaluate the best your options you will need to weigh your organization s priorities as you review the features of each KVMS system Physical Considerations The hardware installed for the topologies dis cussed above come in a variety of packages and sizes System Chassis will range from one U RU or rack unit one RU 1 75 inches to seven U s 12 25 inches and support from one to sixteen computers at the rack The middle pieces KVM Hubs range from ten to fourteen U s with the latest KVM Hub announcement requiring only 1 Unit of rack space Depending on the product User Console Chassis will equally range between one U unit to three U s 5 25 inches supporting one to eight consoles connected to the system backbone Smaller switches implemented with the limited start topology can use as many as seven units of rack space providing support for up to eight con soles connected to thirty two computers Cables will be routed from the CPU s to a local switch chassis Each local switch chassis will be interconnected to one or more central switch chassis or KVM routers before being distributed for multi user access Sometimes local switches at the CPU racks are elimin
142. rom 640x480 resolution to 1024x768 a 15 inch limited bandwidth monitor connected to the KVMS may suddenly fail to display a satisfactory image Changing a config file or Control Panel on the offending platform would correct such a problem without any need for hardware changes or adapters If you have a concern about utilizing a particu lar operating environment with a KVMS consult the KVMS manufacturer or a knowledgeable con sultant with access to up to date information Then be sure to get a money back or model exchange satisfaction guarantee just in case things don t work as expected Computer Hardware Considerations It is easy to mistake O S compatibility for other aspects of compatibility because some computers that use different operating systems ALSO rely on different electronic standards Aside from issues of the proper connector type for mating cables the computer itself can affect compatibility The IBM RS 6000 series which are RISC based computers that typically run the Unix operating system are not compatible with a typical PC KVMS handling Windows or DOS not because of the O S but because of differences in keyboard scan codes or possibly because the particular RS 6000 is being controlled via a serial port not via a graphics keyboard mouse system Some KVMS do handle the different scan codes and some can provide serial control instead of relying on keyboard buffer video display ports DOS
143. round frequency The number of complete cycles per unit of time used for periodic quantities such as alternating current sound waves or vibrating objects Frequency is generally expressed in hertz cycles per second kilohertz megahertz or giga hertz Hertz is often capitalized as it is the name of an individual Henreich Hertz so abbreviations are Hz kHz MHz and GHz frequency response The measure of how the gain or loss of a circuit device or system varies with frequency Generally defined as the passband above and below which the level falls by 3 dB or more relative to the midband level G gain An increase in signal parameter i e voltage current power Gain is a ratio frequently expressed in decibels dB garbage Unwanted incorrect or meaningless information in memory transmission media or other electronic circuit Page 61 ground A connection intentional or accidental between an electrical circuit and the earth or some conducting body e g a chassis serving in place of the earth Also reference level for signals ground loop noise Noise that results when differ ent points of a grounding system are at different potentials and thereby create an unintended current path This can be a problem in KVM extenders and some KVM switches particularly where the devices at each of two locations are connected to AC power sources with different or unrelated ground poten tials Sometimes th
144. rs or HDD 15 built in and DB 15 via an adapter preserving some backward peripheral compatibility the latest G4 Macintosh does not have ADB capability and relies solely on USB for keyboard mouse interface although third party adapters are available to con vert USB to ADB or PS2 type connections In fact there is a growing trend among PC mak ers as well to eliminate so called legacy connec tions for keyboard mouse and other peripherals and to replace these with USB and Firewire connections This is a Smart move because old inefficient drivers are being replaced with modern high speed code and hardware Apple was among the first to promote USB technology Sun Video Past and Present The Sun Sparc platform is a RISC based Reduced Instruction Set Computer workstation or server that typically is equipped with a high res olution monochrome or color monitor Sun has sold their own monitors that match their keyboard buffer video card refresh rates color depth and resolu tion Sun color monitors have traditionally employed special 13W3 connectors with three coaxial conductors and ten additional pins pro viding R G B video as well as two way sense data Such monitors and cables are expensive Some Sun and SGI Video Some who use Sun plat Connections Sun Now forms for servers prefer to Moving to HDD 15 and SGI take advantage of a serial also Uses BNC and HDD 15 output on the Sun unit Sending serial data to a serial
145. rsenide that can serve as an infrared or visible light source when voltage is applied continuously or in pulses LEDs are used as indicators in most KVM switches and may also be used for the transmission of modulated signals in fiberoptic transceivers for KVM extenders LEDs generally have much longer life than lightbulbs can turn on off much faster than other light sources and are responsive to the polarity of the applied voltage link In general a connection between two sys tems or circuits Also a complete network to send and receive data via fiber optics including transmit ter receiver fiber and connectors load The device or element in the electrical circuit that absorbs power and converts it into the desired form such as light heat or motion Page 64 local area network A privately owned geograph ically limited network interconnecting electronic equipment as in an office building to promote dis tributed processing and local communications The LAN is the most common means for interconnect ing computers for the purpose of sharing databases transferring files and allowing multiple computers shared access to printers or to one World Wide Web connection M Mega Abbreviated M A prefix meaning 106 or one million memory random access Abbreviated RAM A storage arrangement from which information can be retrieved with a speed independent of its location in the storage Generally RAM is comprised
146. s System Chassis Multi Console Multi Console Keyboard Video Mouse Keyboard Video Mouse Router Chassis User Chassis Multi Console Keyboard Video Mouse Router Chassis Multi Console Keyboard Video Mouse System Chassis Multi Console Keyboard Video Mouse Router Chassis Multi Console Keyboard Video Mouse System Chassis A ee ee ee Hybrid Figure B Tier 1 left Stars to Tier 2 Tier 2 Stars to Tier 3 but Tier 3 to 4 changes to a Series Connection to chassis hop limitations Combining secondary KVM switches is useful because they provide addi tional buffering amplification for the video sig nal They also extend the reach of the firmware s addressable ports because secondary KVM switches supply their own selection memory and On Screen Display OSD menu s The topologies noted above are representative of global implementations They do not address the dif fering hardware requirements of each system We dis cussed the general variations in hardware implementa tions here For a more detailed description of indi vidual products you may check the web sites or speak with sales associates of the actual manufacturer s For a more accurate evaluation we recommended that you discuss your application with an all product integrator who understands exactly what you are look Multi Console Keyboard Video Mouse Router Chassis KVM Hub User Chassis Dedicated Keyboard Video Mouse User Chassis Dedicate
147. s and a lot of the needed desk space for keyboards If you haven t given it much consideration you might think What s the big deal Why not just stuff a pushbutton or rotary switch with enough contacts and the right sets of connectors into a box and hook it all up Presumably you could then use this gadget to switch a keyboard monitor and maybe a mouse from one computer to the next Actually that s pretty much how early KVMS oper ated well actually the earliest switches didn t need to accommodate a mouse which is why our first edition was called The KVS White Paper Unfortunately this was neither an elegant or a reli able solution For a variety of reasons you ll soon discover the purely mechanical or passive KVMS was very limited and few are still in use Passive KVMS are rarely sold today Instead much more sophisticated active electronic switches dominate the KVMS market We wrote and published the first edition of The Keyboard Video Switch White Paper in 1995 We appreciate the warm reception it was granted by manufacturers media and equipment users alike In the interim many new products and product refine ments have come to the market As in the past we welcome your comments suggestions and correc tions yes we know we re not perfect though we ve done our best to ensure accuracy and fairness We also ask that you honor our efforts and our copy right and not reproduce or distr
148. s half the power relative to the passband D DAC See digital to analog converter daisy chain A group of three or more devices such as K V M switches or circuit elements inter connected to one another in series A cable assem bly with common wires jumpering three or more connections connectors The term is also used as a verb implying to connect multiple devices in series jumpered manner See Series topology damping Reduction of mechanical or electrical energy by means of an energy absorbing medium Damping counteracts resonance or acts to stabilize a state change in a switch Page 57 data base A computer application involving the ordering and manipulation of a large body of data data bus In a KVM switch an independent path for conveyance of video keyboard and mouse sig nals possibly also serial and audio The number of discrete data busses dictate the number of inde pendent consoles that can simultaneously access communicate with different CPUs in the switch chassis data link or path Equipment which permits the point to point transmission of information in data format data path Describes an interconnection between two or more chassis of a KVM switch system through which a console can communicate with an attached CPU Similar to Access Path daughterboard A printed circuit board that is inserted into a connector which is mounted onto another pc board motherboard A board to board
149. s the last chassis in the sequence is fitted with a terminator The Series model is used in many single console KVM switches supporting a dedicated port for expansion but only one multi console KVMS system requires the Series model some others support it but don t require it Multi Console Keyboard Video Mouse Switch Chassis System Chassis System Chassis The Series Architecture is the Most Simple and Easy to Implement Multi Console KVMS Architecture Limited Star The Limited Star Model is popular for smaller capacity KVM switch systems single or multi con sole The connection between the first chassis and subsequent chassis originate at the first chassis to which the console s 1s connected This topology model is deemed limited because it is scalable on a single tier only KVMS that depend on the Limited Star model typically use system ports computer connection for expansion purposes To establish a single data path between two chassis a connection is made from a system port on the first chassis to a console or user port on the second chas sis KVMS systems that use the Limited Star model have limited CPU capacity a few such systems mix Limited Star in conjunction with another topology to somewhat expand capacity If you have a large number of CPUs or plan to in the future don t use a Limited Star system See diagram which follows Page 36 Multi Console Keyboard Video Mouse User Switch Cha
150. set the and which provide Jumpers rotary or DIP Dual 10 data bit color depth be returned to the operating system Inexpensive mechanical adapters connect in the connected Mac computers Monochrome CGA Uniform Resolution Map Monochrome Q F C O 5 5 D D O oc E z 2 Q 5 5 e e lt O O The CGA Color Graphics Adapter card gave us up to four colors displayed at a resolution of 320 H x 200 V or it could be switched to operate in single color mode at 640 H x 200 V pixels Thus you could sacrifice color depth in favor of resolu tion where that was desirable 1 e for text display oO m e l O O S o I D O O d O gt 1 POs D DE So 13382 om 303841 on SF Basses ws lt lt OQ u Se O 2 O 3 S Q2 O D 5 o 8 8 5 ES 3D oe E S R 5 2S 0572 8023255057 E A o 352050 S 6 EP 5A oo A 3 280 YS Soon gat E A S B F mE 28 5 8q tlic NE oss Z na Se onuraz lt E 5 E N 20 3 OD er n D O Ses Seto Skaki eke y S55958324582 298828 2767 PN z S gt H gt u3 2 8458555582380238 LUISE a 522228588 erage DSSS RRAS ERESSE v 3r52 8nd2 55 888782 52 uss A gt n 7 0 BESO oS D HO aH oe eS V QQ 73 O lt r O Qo as n 5 SS Serp DES Sts Soet9sd2853e0gR3983 45r4 P a 2 Q S 5 S Qg Pon Soag Ase eapvpsda sevseeyo LIP BASOA DN gt Z 5 E O 5 E RE lt BS DO noo S V o O O o S OE SF
151. simple single console switch yet larger scale KVM switching including the possibility of enterprise wide implementations may improve the overall productivity of the I T department Consider all pertinent factors when you evaluate a KVM switch system factors that range from the way hardware is physically deployed to how people work with the hardware Be sure you understand the large scale KVM solutions even if they are not your first choice now due to budget or modest require ments Bear in mind that though you may initially purchase single console switches for small groups the models and designs you acquire now will have economic significance later when you migrate to a multi console system in short plan ahead Single vs Multi Platform KVM Switches Many KVM switches support only one type of computer PC Mac Sun etc Increasingly switches are available that support more than one type of computer Some handle Sun and PC Some handle Mac and PC Some handle multiple types of plat forms If you work with more than one type of computing platform and want more information see the sections on What If You Have a Mix of PCs and Serial Terminals and Platform Support under Multi Console KVMS Systems The New Standard Page 17 Page 18 Product Function for the Technically Oriented Reader You don t have to understand anything about keyboard scan codes video circuitry emulation or bus architecture to use a KVMS effecti
152. site Sync and to convert between various keyboard and mouse coding schemes This circuitry makes it possible for a single device to offer cross platform switching capability Without special provisions video cannot travel over long cables because these high frequency sig nals become distorted by the reactance of the cables Reactance is an electronic characteristic that is present in all cables and the longer the cable the more it will degrade a high frequency waveform It is possible to reduce the degradation caused by cable reactance by a using higher quality controlled impedance cables b using buffer and booster amplifiers and or c converting the electri cal signals to light and using fiberoptic instead of copper cables Keyboard and mouse signals are not Page 14 as high in frequency as video yet they still don t travel well over long distances due to timing issues the capacitive reactance of a cable will slow down the signal causing a delay in acknowledgment or handshake which can cause the link to time out and produce an error or a frozen system Mouse coding is sent in packets and smeared timing in the delivery of these packets can result in misinterpreta tion of mouse input by the computer Some active KVMS products with or without adapters provide for buffered signal interfaces that is they intercept and amplify the signals making it possible to extend up to several hundred feet the
153. specific definitions of switching bus and data paths elsewhere in this docu ment if you have not already done so As a refresher we define a console as a key board video monitor and mouse although in some KVM systems there may be no mouse while in others the console may also include audio speakers and or microphone or even an RS 232 serial termi nal or other device In short the console port is one set of connections for a user to control con nected computers Some multi console KVMS designs allow the output video of a single computer port to be displayed on multiple console monitors simultane ously concurrent access while others do not no switch allows simultaneous keyboard mouse input from two console ports to one CPU because the computers themselves are not equipped to deal with such input it is always sequential Where concur rent access is available the maximum number of consoles that can access a given computer system ranges from two to sixteen Remember that this value refers to the number of consoles accessing the same CPU larger multi console KVM systems can have many dozens to hundreds of consoles operat ing simultaneously and accessing different CPUs Unified Versus Split Bus Architecture Until recently most KVM switches routed the video keyboard and mouse signals along similar simultaneously switched pathways A few of the newer multi console KVM switches depart from this tradition and rout
154. ss time than it takes the operator to stand up much less walk 5 or 50 or 500 feet to another computer as would be required without the KVMS Because there are fewer monitors and key boards there are fewer components to be main tained This saves time and money in the long term over and above the direct acquisition costs or power costs In situations where a single operator would otherwise be working in front of multiple CRTs the KVMS instead lets the operator work with a single ideally placed monitor and keyboard This will reduce RSI repetitive stress injury so that the KVMS actually saves an unspecified amount in direct and indirect medical and workman s compen sation costs This also positively impacts workforce productivity Particularly in small office environments the KVMS goes a long way toward reducing visual and physical clutter The cleaner neater layout facili tates operator concentration thus improving produc tivity When you are dealing with personnel earning 50 000 to 150 000 annually a few percent greater productivity can add up to a lot of dollars annually possible enough to pay for the KVMS in the first or two of operation Page 48 Finally the greatest hidden savings may be that the KVMS allows you to stay in the current space and avoid a costly move or build out It is not unusual for the installation of KVMS to cut floor space requirements down to one half or one third of an unswitched
155. ssis Chassis Multi Console Multi Console Multi Console Multi Console Keyboard Video Mouse Keyboard Video Mouse Keyboard Video Mouse Keyboard Video Mouse Switch Chassis Switch Chassis Switch Chassis Switch Chassis System System System System Chassis Chassis Chassis Chassis The Limited Star Architecture is a Popular Multi Console KVMS Architecture for Smaller to Mid Capacity Systems Expanded Star of the primary legs KVMS system architectures devel primary leg Y The Expanded Star topology resembles a Limited oped on the Expanded Star model will typically use Star model but offers extended functionality Category 5 cable for interconnectivity between system This Topology model is deemed the Expanded components KVMS systems based on the Expanded because of it is scaleable across more than one tier architecture provide high level support for consoles and and to a greater number of CPUs It may also include computers may combine a high capacity middle piece provisions to connect a Limited Star model to any or all 2 usually include redundant emulation support System System System System Chassis Chassis Chassis Chassis CPU to KVM CPU to KVM CPU to KVM CPU to KVM Switch or Ext Tx Switch or Ext Tx Switch or Ext Tx Switch or Ext Tx 4 3 2 1 CPU to KVM Switch or Ext Tx 5 System Multi Console Chassis Chassis KVM Hub Se as to KVM Switch or Ext Se as CPU to KVM e Switch or Ext Tx 48 or more ae 6
156. systems components may require dedicated racks while others can be co located in the racks with computers In some cases the KVMS hardware may extend beyond the data center walls We have tried to demystify some of the gener alities for you by identifying four primary switch topologies We also provide a general overview of current component sizes and functions although it is not our intention here to describe specific products Neither is it our intention to supply here specific Multi Console Keyboard Video Mouse Switch Chassis System Chassis Multi Console Keyboard Video Mouse Switch Chassis User System Chassis 3 Multi Console Keyboard Video Mouse Switch Chassis system design concepts we do generally describe how to optimize the functionality of any KVMS system The topologies covered here focus only on the basic architectures and not myriad combinations and permutations that can evolve in specifically designed and installed systems The three basic topologies are Series Star and Expanded Star Certain model KVMS may be con figured in more than one of these topologies When more than one topology is mixed in a given system that becomes a fourth topology the Hybrid Series The Series model is a simple to understand and easy to implement topology All connections are made in line series with the first chassis connected to the second chassis and the second to a third chassis and so on In some model
157. t degrade signal transmis sion reflection coefficient The fraction of light power reflected backward at the fiber end face of a fiber optic cable This accounts for about a 2 to 3 dB loss typically register A memory device capable of containing one or more computer bits or words Page 70 relay An electrical device that is designed to inter pret input conditions in a prescribed manner and when specified conditions are met to respond by causing contacts to operate or by causing circuits to open or close Inputs are normally electric but may be thermal mechanical or by other modes A relay is an electrically operated switch relay contact bounce Undesired intermittent clo sure of open contacts or opening of closed contacts This may occur either when the relay 1s operated or released or when the relay is subjected to external shock or vibration The term bounce is normally associated with internal causes repeater A device that receives amplifies and otherwise reconditions and retransmits a signal Some KVMS switches use repeater circuitry to con vey control and video signals over longer distances from chassis to chassis resistance The property of a body which opposes and limits the passage of a steady electrical current through it resistor A circuit component which offers resis tance to the flow of electric current Its electrical size is specified in ohms or megohms 1 megohm 1 000 00
158. t zero volts when both inputs are at zero volts It must also be capable of accepting negative feedback without oscillating Some video drivers use Op amps optical fiber Also called fiber optic cable A thin flexible glass or plastic fiber capable of transmitting light over considerable distances by internal reflec tion OSCAR An acronym trademarked by Apex PC Solutions for on screen configuration and report ing Apex version of an OSD for KVM switching oscillator A device or circuit for producing elec tric oscillations specifically a radio frequency or audio frequency generator Used in computers to generate the clock by which operations and data transfers are timed and defined OSD Acronym for on screen display In a KVM switch this is an optional feature that allows selec tion of computers by means of menus displayed on the monitor Typically connected computers are given names on the OSD then selected by name as contrasted to the use of direct pushbuttons step through pushbuttons or keyboard escape com mands OSD s vary by manufacturer and many also include security features password access Out of band In the context of this document this refers to the control of a computer which does not rely on access to it via a modem or LAN WAN connection See in band P packet switching A data transmission process using addressed packets of data whereby the com munication channel is occupied o
159. tage drop The voltage developed across a component or conductor by the flow of current through the resistance or impedance of that com ponent or conductor Often simply called voltage Also called drop The voltage across a resistor is usually called IR drop while that in a conductor is usually called resistance drop voltage regulator A circuit capable of generating from a varying input voltage a constant output volt age to a varying load current vswr Abbreviation for voltage standing wave ratio See also standing wave ratio VW 1 A flammability rating established by Underwriters Laboratories for wires and cables that pass a specially designed vertical flame test for merly designated FR 1 W wafer A thin polished slice of single crystal silicon on which monolithic integrated circuits are fabricated Page 76 WAN Acronym for wide area network Similar to a LAN local area network but extending beyond the physical boundaries of a single building or a small physical area WANs may take advantage of internet links private telecommunications links microwave or infra red relay or extended gateways between multiple LANSs to link more distant com puters for the types of access normally provided by a LAN watt Abbreviated W The practical unit of electric power In a dc circuit the power in watts is equal to voltage multiplied by current In an ac circuit the true power in watts 1s effective volta
160. taneously and by the same amount relative to ground Common mode EMI can induce noise or unwanted signals when various systems KVM switches extensions and computers are intercon nected common mode impedance coupling The cou pling of energy from one circuit to another that results when two or more currents flow through a common impedance components Any items used in conjunction with another item in its manufacture concentric A central core surrounded by one or more layers of helically wound strands in a fixed round geometric arrangement Different diameter circles with exactly the same center point conductivity The ability of a material to conduct electric current usually expressed as a percentage of copper conductivity copper being 100 Con ductivity is expressed in terms of the current per unit of applied voltage It is the reciprocal of resis tivity conductor Wire or any method used by electricity to go from one place to another conduit Usually a metal covering to go over wire to protect it from damage connector A coupling device employed to con nect conductors of one circuit with those of another circuit Used to provide rapid connect disconnect mating with a pc board posts or another connector A housing becomes a connector when it contains the specified number of contacts with conductors to make it functional connector assembly Includes more parts than just a housing and contacts
161. tching and Extension V 2 0 1a Page 51 Appendix B KVMS Glossary A ADB Apple desktop bus A connector and signal standard developed by Apple Computer for use in their original Macintosh series of computers ADB is primarily intended for keyboard and mouse but also supports such items as dongles modems and graphics tablets ADB is more recently being replaced by USB connections on iMac G3 and G4 series Apple computers ac Alternating Current An electrical current that reverses its direction of flow at regular intervals ac 60 hertz cps means reversing direction of flow each half cycle or 120 times per second Access path restrictions In a K V M switch this refers to a limitation on the number of users con soles which can simultaneously view control differ ent computers The restriction to access for viewing or controlling is due to limitations in the number of data busses in a given switch chassis or a limitation in the number of discrete data paths between switch chassis 1 e the paths for data active element Those components of a circuit that have gain or direct current flow They change the basic character of the applied electrical signal by rectification amplification switching etc Exam ples include diodes transistors and SCRs A D converter Analog to digital converter Cir cuitry which accepts a continuously varying voltage or current input and converts it to a digital output T
162. terminal does not produce the same high resolution high data rate image but for a server this is often perfectly accept able and the advantages are not only a cost savings in the monitor but also reduced demands on the CPU for video I O input output functions freeing the CPU to do a better job of serving Another potential benefit of serial video keyboard control via a terminal connection is security against hacking 13W3 Connector Used for Page 10 by virtue of an non breakable administrative control path Switching Sun video has required a switch that is capable of sufficient bandwidth and that has the proper connections to accommodate the Sun moni tors The Sun keyboard layout and signals are also different from PC or Mac which is why early KVM switches could not mix Sun with other platforms in fact most still cannot do this Around 1995 KVM switches began to appear that could accept Sun keyboard mouse lines and in some cases translate them to PC keyboard mouse while passing the Sun video through to a high resolution SVGA monitor Other KVM switches dealt only with Sun video and keyboards and did not accommodate PCs Sun is now shipping com puters that still use a proprietary keyboard mouse connection but which have conventional HDD 15 SVGA video output we believe this change began with the Sparc 5 Ultra Enterprise series This means that a KVM cable meant for one Sun plat form may require an
163. th 640 x 480 1 x 60 18 4 MHz If you take the total time available for a horizontal scan line and the corresponding retrace and divide this by the actual time used to display pixels you get a factor of 1 45 when multiplied by 18 4 this yields 26 7 MHz Similarly the wasted time in ver tical retrace yields a factor of 1 03 resulting in 27 5 MHz actual video bandwidth Today though 17 inch monitors are the most common size in the data center and office environment and you ll often see these monitors set as high as 1024 x 768 pixel resolution A monitor in this display mode with an acceptably low flicker 75 Hz refresh rate will have a video bandwidth of 1024 x 768 x 1 45 x 1 03 x 75 88 MHz Higher resolution images used in graphics and video effects work often run on larger monitors at 1600 x 1200 pixel resolution at 75 Hz to 100 Hz in which case the bandwidth require ments can exceed 250 MHz Few KVMS systems can accommodate bandwidth as high as even 150 MHz so if you are switching in a graphics intense environment check the KVMS video speci Page 25 fications carefully See the full page illustration of Resolution vs Bandwitdth which follows Interlaced monitors monitors with a lower refresh rate will flicker more you may notice this if you move your eyes quickly chew gum while viewing the screen or view from a distance The larger the screen or at least the higher the reso lution the higher the act
164. the data was set to pass through the KVM system to the connected user peripherals only when they addressed a specific computer The concept of emulation is thus fairly straight forward Indeed in the PC world there are only a handful of chips used to support keyboard and mouse interface Nonetheless the implementation of emulation for a KVMS manufacturer is less than simple For one thing there are many variations in keyboards and mice some involving timing issues some involving scan codes and other involving data format What keyboard and mouse will actu ally be used with a given KVMS The KVMS manufacturer cannot generally specify this and so the product must be broadly compatible On the other end each computer manufacturer has options as to which physical devices to support which chip or chipset to use inside the computer and what coding and protocol options to utilize Again the Page 42 KVMS manufacturer must try to accommodate the broadest possible spectrum of devices and options All the above considerations multiply many fold when a KVMS is built as a multi platform capable system In such cases the switch now must support different connections widely different coding see_ the details of keyboard and mouse coding in the technical explanations of this document and in many cases it must add emulation of monitor sense data As you may know from reading the sections of this document dealing with the Details
165. the frequencies that can be transmitted or received For a transmission system it is typically the highest frequency transmittable assuming the lower ones can usually be handled A circuit that passes frequencies from 1 000 Hz to 10 000 Hz can be said to have a bandwidth of 9 kHz The limits of the band are generally defined as those upper and lower frequency points beyond which the signal level is attenuated by 3 dB or more relative to the middle of the passband baseband signal A signal transmitted at its origi nal frequency without modulation or multiplexing baud A unit of signal speed the reciprocal of the shortest bit interval Sometimes equivalent to bits per second bipolar A circuit which utilizes positive and nega tive power supply voltages Typically low power amplifiers may use ground and a positive power source of 3 to 12 volts whereas a higher power amplifier may use ground and both pos and neg power supplies Line driver amplifiers that are made to send signals down very long cables often use bipolar circuitry Birmingham Wire Gauge The Birmingham Wire Gauge BWG was used extensively in Great Brit ain and the United States for many years but is now obsolete Its use is now limited though it is sometimes used with galvanized steel wire for cable armor Generally AWG applies in K V M and com puter circuitry bit The smallest element of information in binary language A contraction of BInary di
166. the wheel mouse SGI Silicon Graphics has employed a several different keyboard mouse standards In one imple mentation they employ a standard PS2 connector but it is wired using two pins not used in PC s so that the keyboard and mouse both share a single connector In other implementations they use con ventional PS2 keyboard and PS2 mouse wiring with separate connectors In still others they have used DB 9 or DB 15 connectors for serial keyboard and mouse I O Sun workstations use a completely different type of mouse 3 button and some with optical scanning instead of a rolling ball and the Sun mice have dif ferent connections 8 pin Mini DIN bussed through the keyboard and unique driver software Sun Mac and PC mice or trackballs are not interchangeable electronically Even though some manufacturers offer mice or trackballs for the differ ent platforms that differ externally only in their con nector configuration a connector adapter wouldn t necessarily allow a specific model to be used on a different type of computer format conversion is necessary too Kensington Trackball Page 12 Alps Trackpad Some newer computers have introduced a fur ther complication for KVMS systems the Universal Serial Bus USB Compaq Dell IBM Apple SGI and other leading manufacturers now sell com puters that can be controlled by USB connected keyboards and mice More manufacturers are join ing this trend abandoning l
167. ther way a check that tests whether the number of l s or 0 s in an array of binary digits is odd or even Some RAM chips include parity checking to reduce the chance of undetected random errors Page 67 passive components Circuit components which have no gain characteristics such as capacitors and resistors PCM An abbreviation for pulse code modulation A scheme by which an analog signal is sampled and converted to a digital signal for transmission or storage peripheral equipment Equipment separate from the main computer includes all forms of attach ments to main computer systems User peripherals in a K V M switch system include typically the keyboard video monitor and mouse pico A prefix meaning 10 12 or one trillionth polyvinyl chloride PVC Thermoplastic com pound composed of vinyl chloride polymers Blend ed with other polymers or copolymerized with monomers to give abrasion resistance heat stability short molding cycles and low shrinkage This is used as an insulation in some wires and cables while it is flexible it may not be as durable as rub ber in constantly flexed cables and it is not suitable for use in plenums due to its flammability and the toxicity of the smoke it generates when burned positive lock A type of latch or locking mecha nism that engages in such a way that the parts cannot be unlocked accidentally Used to inserts in shells connectors in mated position contacts
168. tivated consoles in the same sys tem may also be connected via Cat 5 extension tech nology When switching is initiated at the computer hardware console access is authenticated before the console can select any given computer within the KVM switch Again the middle section provides KVM signal routing but as noted above this sec tion of the KVMS system may or may not provide the primary switching functions Some large KVMS switches may require an additional external hard ware component that uses software to manage the KVMS or it may serve to simply connect one hard ware address to another hardware address console to computer One recent manufacturer s recent announcement and release of a new multi console KVMS system may be characterized as simply a Star model But if the new product is combined with the already existing Limited Star model available from this pro ducer the new product can be implemented with much wider concept to resemble the Expanded Star model or Hybrid model There are inherent benefits to each approach and your optimum system will depend on a few variables These variables include but are not lim ited to the level of protection from component fail ure the level of redundancy and your approach to implementation Whether the KVMS system is to be installed prior to the hardware all at once or phased in with the computer hardware will help narrow your options Large KVMS systems can concentrate dist
169. ual horizontal sync fre quency for a given refresh rate Rapid refresh rates for stable low flicker images and large high reso lution images require ever more video bandwidth which requires faster more costly circuitry and higher quality controlled impedance cabling This is why a given switch that works acceptably with VGA may degrade an SVGA or an XGA image BEGINNING BEGINNING BEGINNING OF FIELD 2 OF FIELD 1 OF FULL SCREEN SCAN Video Scan Line field 1 Video Scan Line Horizontal Retrace Horizontal Retrace INTERLACED NON INTERLACED Interlaced Video left is Most Often used for Television Whereas Non Interlaced Video is Generally for Computers KVMS Video Signal Processing A KVMS made strictly for PC switching should provide video buffering for more stable on screen images and longer video card life The signal enters the KVMS after emerging from the various com puter display card outputs Ideally the KVMS buf fers and terminates the video signals then passes signal from the selected computer to the monitor Technically this is merely amplification not signal processing When mixing computer platforms the KVMS may not only buffer the video it may also translate the signals from the various computers to work with a single monitor Mac and Sun platforms may have vertical and horizontal sync frequencies that differ from PCs In some cases a multi sync monitor can handle conversion between video sync f
170. uters at the same time and they will all boot at once rather than sequentially one at a time Switches that have such emulation are known as automatic booting switches for this reason They reduce the incidence of hung systems during opera tion too because each computer thinks it is con nected to a keyboard whether or not you have actu ally selected the computer with the switch If you want to read more about emulation see the Section on Emulation Services How Does the Active KVMS Work As we have said the active KVMS emulates the presence of a keyboard to each computer The origi nator of keyboard scan codes IBM defined three Scan Sets Scan Set was for the XT computer Scan Set 2 was for the AT architecture and Scan Set 3 was for 3270 terminals which shared the same keyboard layout as PCs Most clone vendors use Scan Set 2 AT whether or not the keyboard has an AT style 5 pin DIN or PS 2 style 6 pin mini DIN connector IBM and a few other vendors instruct the keyboard to switch from Scan Set 2 on power up to Scan Set 1 which lets them elimi nate the keyboard translator microprocessor on the motherboard Earlier PS 2s Model 30 through Mid Model 70 use Scan Set 2 while later PS 2 models such as Model 80 85 90 95 and 77 use Scan Set 1 Some RS 6000 and Silicon Graphics machines use Scan Set 3 The real issue is whether the KVMS can handle all three scan sets just like the IBM 101 key keyboard This
171. various computers do so in a fixed sequence and at uniform dwell times dwell is the amount of time a given computer stays selected other KVMSs let you select a subset of computers to be scanned let you arrange the order in which they are scanned and let you set different dwell times for each computer so that you can spend more time viewing the most important to see platforms To halt scanning when you see a screen requiring your attention you may have to press a button on the KVMS use a keyboard command or simply touch the mouse or keyboard The point once again is that you should look carefully not only for the presence of a feature but at how the feature is implemented Other Issues to Consider When selecting a KVMS consider its behavior with regard to switching delays video glitches proper operation of ALL keyboard features caps lock and num lock indicators for example correct mouse response and tracking and overall reliability Also consider whether it is possible to expand the number of switching channels without having to add another monitor and keyboard Does the switch allow for an expansion chassis Do you lose a port Page 34 on the base unit when you add an expansion switch and how important is that in the context of the overall system Do you have to operate multiple switch controls after expansion or do you retain single point computer selection capability These are important considerations that may
172. ve a shared VGA monitor it is necessary to strip the sync from the green Mac video line then regenerate it for proper feed to the VGA monitor s sync line As we mentioned previously the KVMS or an adapter must also return a code to the Mac indicating the resolution and color depth of the connected monitor Digital Signal Monochrome MDA 720H x 350V 1 Color CGA 640H x 200V 1 Color Mode CGA 320H x 200V 4 Color Mode EGA 640H x 350V 256 Colors Newer format color images Either extended VGA type analog Page 30 Analog Signal Color or Gray Scale VGA 640H x 480V 256 Colors SVGA 800H x 600V 256 Colors SVGA 1024H x 768V or 1280H x 1024V 256 Colors or new type digital USB or other digital format Ultra High Res Note Conventional NTSC HDTV Ready television has a 3 4 1 33 1920H x 1200V aspect ratio whereas HDTV 16 7 Million Colors has a 9 15 1 78 aspect ratio XGA II 1280H x 1024V 16 7 Million Colors Very High Res 1600 H x 1280V 16 7 Million Colors This Summary of Common Video Resolution and C
173. vely On the other hand if you are designing specifying or troubleshooting a KVMS the more you know the better your chances of success We have written this section of The KVMS White Paper for those of you who are interested in the nitty gritty details of this technology up to a point we don t get too involved with the finer points of circuit design If all the detail that follows whets your appetite for more information or if you would like to have a live presentation to explain what we ve written here contact the authors of this paper about attending one of our KVM Technology Seminars or having us schedule one especially for your organization Keyboard Switching The old IBM PC XT keyboard was a 1 way device It generated signals that went to the comput er The IBMPC AT and subsequent platforms used a two way data path with the computer probing the keyboard as well as the keyboard sending keystroke data to the computer To be effective the active KVMS must emulate the presence of the keyboard to the computer when that computer is not selected on the switch As indicated previously not all scan codes are the same and timing is less than well defined in the so called standard so the emulation can be tricky Store and forward technology is used for improved emulation in some switches Until recently most PCs used one of two different types of keyboard connectors IBM s older PC AT style keyboard had a 5 pin round conn
174. very flexible plasticized backing coated with metal lic conductors processor The computer especially in data sys tems involving a number of peripheral devices fre quently referred to as the central processing unit CPU That portion of a digital computer which performs the arithmetic logic and system control operations production model A model in its final mechani cal and electrical design form and manufactured using production tooling and methods as contrasted to a prototype demo or pre production model program The set of instructions that the computer is directed to carry out in a specified sequence Also a verb to indicate the process of instructing a computer or a device such as a KVM switch to function in a particular manner PROM An acronym for programmable read only memory A ROM that can be programmed once but then cannot be reprogrammed propagation delay Time required for an elec tronic digital device or transmission network to transfer information from its input to its output Also refers to a delay in distribution of a new or changed domain name to IP address assignment across the internet propagation delay time The time between the application of a digital input waveform and the cor responding change in output waveform It 1s mea sured between reference points on the waveforms The time is generally different for positive going and negative going waveforms A difference in the propa
175. vinyl chloride Page 69 Q queue Waiting lines resulting from temporary delays in providing service In computer related systems a queue can be a string of instructions or data stored in a buffer and awaiting execution or transmission QUIP An acronym for QUad In line Package A packaging technique similar to a DIP but having two rows of pins along each long side or a total of four rows R R Symbol used to denote resistance in ohms rack A cabinet used to house components which permits convenient removal of portions of the equipment for repair or examination Original racks were standardized steel frames for mounting19 inch relay panels in telephone exchanges Today racks vary in size and shape to meet the specialized requirements of computer aircraft military elec tronics and test equipment manufacturers The nominal width of a rack refers to the width of the front panel of equipment to be mounted on the rack rails typical widths are 19 23 24 and 30 inches Rail hole to hole spacing is most often specified by the EIA electronic industries association random access memory RAM See memory random access raw data Data which has not been processed may or may not be in a computer compatible format RC Designation for any resistor capacitor circuit or a circuit which exhibits the characteristics of resistance and capacitance since it may not have discrete resistors or capacitors read To cop
176. ween being able to fit the lab in your current facility or having to look for a new building Additionally you need only refer to the prior discussion for LAN Administrators to understand that the equipment and maintenance cost savings apply equally in the lab Some KVMS manufacturers provide the ability to remotely locate the KVMS from the computers or to allow dual or multiple operators access to the same KVMS connected computers With remotely located access to the switch it becomes possible to bring a lab full of computers to the developer s office desk where they can be accessed and reboot ed by a single keyboard and monitor without hav ing to use any network hardware or software you get to the blue screen boot with out of band KVMS unlike LAN software or in band server access solutions Is KVMS for every situation Frankly no However there are many ways to approach KVMS and we encourage you to evaluate it carefully with currently available technology to make sure you are taking advantage of the best technological solution to your needs What If You Have a Mix of PCs and Serial Terminals Currently if you have to access data processing resources via serial or dumb terminals and com munications lines and you also have to access serv ers or workstations locally via video and keyboard connections you must have at least two monitors and keyboards often many more Products have
177. within a few months That s because generic chips and circuit boards are avail able from original equipment manufacturers to per form the basic switching functions or in fact all of them However all the many variations in keyboard and mouse and to a lesser degree video standards are quite difficult to accommodate in a single prod uct The more experienced manufacturers deliver KVM switches with robust emulation services They have had the benefit of the finances staff and other resources to acquire and evaluate the many different computers and peripherals Issues of timing and waveform and poorly defined specs cannot be resolved by web searches and data sheets alone they require hands on testing and documentation Better KVM switches incorporate custom pro grammed firmware that is periodically upgraded and is ideally field upgradeable to remain compat ible with current devices and operating systems This is why one must be wary of any switch not being offered by an established primary KVM manufacturer Anyone can put a label on a box and many do but few can back that product with the design expertise and technical support that you should demand from a device that can bring your server farm to a standstill if it doesn t work prop erly Page 23 Page 24 A Video Refresher Before you can truly understand the way KVMS products handle video you must understand the types of video that are found in today s co
178. wn region provides high impedance to applied voltages of less than breakdown magnitude When breakdown voltage is reached an avalanche effect causes the device to conduct with virtually no impedance zero voltage switch A circuit designed to switch on at the moment the ac supply voltage crosses zero This technique minimizes the radio frequency interference generated at switch closure ZIF Zero Insertion Force A component designed to eliminate the insertion and withdrawal forces during engaging and separating Page 78 Who Created This Document The KVMS White Paper was originally written and revised by Anthony A De Kerf president of Tron International Inc and by Gary D Davis pres ident of The WorkCenter Corporation Both firms have specialized in designing com puter rooms and testing labs since 1989 with an emphasis on the use of Keyboard Video Switches to maximize the capacity of available floor space and optimize work flow In fact when the concept of Keyboard Video Switching was in its infancy with only a few available brands Tron International was a pioneer in the installation of KVMS products in large computer labs and multi server environments Today both firms provide engineering sales installation and technical support services for a variety of manufacturers KVMS products When you consider the use of a KVMS it 1s important to know if the manufacturer provides related products such as shar
179. y usually from one form of storage to another particularly from external or secondary storage to internal storage to sense the meaning of arrangements of hardware to sense the presence of information on a storage medium read only memory ROM A storage arrange ment primarily for information retrieval real time operation Solving problems as fast as they occur so that the results can be used to guide the operation Transfering data immediately as it is generated rather than from stored information receptacle In coaxial RF connectors the recep tacle is usually the fixed or stationary one that is mounted on a panel In shell type multiple contact connectors the receptacle usually contains the pin contacts and is mounted on the cold side of the circuit such as in a drawer or black box Recep tacles mate with plugs record noun A line of information under a col lection of fields redundancy Any deliberate duplication or partial duplication of circuitry or information to decrease the probability of a system or communica tion failure Ina KVM switch system design redun dancy can help assure continuing control of con nected servers despite the failure of one or another KVM component reflection The backward transmission of elec trical energy caused by a change in impedance Splices or non optimized extension connections in high frequency cables such as video can causes unwanted reflections tha
180. y differ here we have not thoroughly researched this new interface Like the Macintosh the Sun keyboard and mouse share con nections via a common bus although the busses are different and Sun uses different coding and connec tors than does Apple In addition to consideration of scan codes and connectors as previously discussed keyboard power specifications are also an issue The switch must apply the correct power to the connected key board remember keyboards contain active circuit ry In some cases the switch itself 1s powered by the keyboard output power of connected computers so there must be compatibility in that specification too Most PCs have 5 volt keyboard power output typically delivering 0 75 to 1 amp of current A few KVMS models are powered by the computer s keyboard output and will not function reliably or at all if the computer does not meet the design specifi cation this is seldom a real problem though Some early AT amp T and Texas Instruments computers had 12 volt keyboard circuits with 9 pin D connectors TI had one model with a 5 pin DIN that used 12 volts Some Dell computer keyboards operate at under 5 volts and some IBM PS 2 models cannot deliver as much as 0 75 amperes though they are adjustable internally While most KVMS systems today are not powered by the keyboard power out put at least one model senses the presence of a CPU by virtue of sensing keyboard power presence And on the
181. z a Tae CA P i ar Les f i F 2 J Bis F a r j E ei _ ay f i H RE N 7 l INTENTIONALLY LEFT BLANK Contents Whatis KVM SWC Fe oo he eh oo heh hE SH bh SESH S Rd RE i SEFERE Ri 1 What Are KVM Extension ProdUCtS 2 c c ccc ccc ccc 2 Why You Should Be Using These Products 42 dc ccc doe ccc 3 e Facilities Managers Can Save Space and Power and Improve Work Flow 3 e LAN Administrators Can Save Time Simplify Management and Fit More in Available Space 3 e Benefits to Software amp Hardware Developers c c ccc 5 e What if You Have Dumb Terminals c c 6 e Addressing a mix of PCs RS 6000 Mac Sun HP Dec Alpha SGI and or other Platforms 6 e Office Settings Gain Security and Save Space with KVM Extension and or Sharing 6 Video amp Keyboard Circuitry A Non Technical Overview _ c c c 8 NCO oy oo io oes a ht erie CORRA RRR arse ae asin aerate se ant E ERA R RAE and A 8 e Digital Video for PCs cc c c 9 e Analog Video for PCS acs cesnpaedsseinaessi obion M a a h 2 cn 9 e MacintoshVideo PastandPreseNM c c ee ee eee eee eee nes 9 e Sun Video Past and Present 0 0 ce ee ee ee ee eee eee eee eee ees 10 SOIL VIO faeces oes bese 4 ae ne ne Sans Gene o amen ne bans Sond 2 ane R te bone eae e e

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