StudioTech M46-00180 Network Router User Manual
Contents
1. DC is not detected on either pin 200 ohm terminating networks are applied to those same pins This ensures that the Model 46 s hybrid circuitry remains stable preventing objectionable audio signals from being sent to the 4 wire output con nectors One caveat does apply there may be a few seconds of severe noise whenever an interface moves from a DC present condition to a DC not present condition But other than that period the audio paths will remain clean Model 46 User Guide Studio Technologies Inc As a visual aid LEDs on the front panel will display the DC power status of pins 2 and 3 But when auto terminate disable mode is active the LEDs will no longer indicate the intercom circuit s termination status For special externally powered 2 wire ap plications the auto terminate function can be disabled This primarily will come into play when splitting the Model 46 s re sources into four separate single channel interfaces Moving advanced configuration DIP switch 1 located on the Model 46 s back panel to its on up position disables the auto terminate function To someone observing only the Model 46 s front panel this change would not be readily appar ent The front panel LEDs will continue to display the DC power status of pins 2 and 3 But whether or not either or both LEDs are lit the Model 46 will never apply 200 ohm terminations to pins 2 or 3 For the hybrid circuits to remain stable termin2. Position Modular Plug RJ 45 to Artist Matrix Port 108 N Model 46 4 Wire Output XLR F To Model 46 4 Wire Input XLR M Back Panel Jack on Matrix Chassis Pr3 Pr2 Pri Pr4 YvvY vv Y 12945678 Jack Front View T568B RJ 45 Wiring Pin 1 WHT ORG Pin 2 ORG WHT Pin 3 WHT GRN Pin 4 BLU WHT Pin 5 WHT BLU Pin 6 GRN WHT Pin 7 WHT BRN Pin 8 BRN WHT 8 Position Modular Plug also known as RJ 45 Pr3 Pr2 Pri Pr4 YvvY vv vy 12345678 Plug Top View Release Tab on Bottom Issue 2 September 2007 Page 30 Model 46 User Guide Studio Technologies Inc Appendix C Interfacing Clear Com Matrix Intercom System Analog Ports with the Model 46 Interface Model 46 Call Receive 1 Call Receive 2 Audio Receive 8 Position Modular Plug Audio Send 4 To Model 46 RJ 45 to Audio Send 5 4 Wire Input Matrix Port XLR M Audio Receive 6 Call Send 7 Cal Send 8 To Model 46 4 Wire Output XLR F Model 46 User Guide Studio Technologies Inc Issue 2 September 2007 Page 31 4 WIRE INPUT INTERFACE 1 CHANNEL 1 0 4 6 8dBu XLR F 4 WIRE INPUT INTERFACE 1 CHANNEL 2 0 4 6 8dBu XLR F 10K 10K BAND PASS FILTER NE 10K 10K 100Hz BkHz CIRCUITRY IDENTICAL FOR INTERFACES 1 amp 2 B
3. also be connected Many broadcast applications use the dual channel TW series from Telex RTS including their popular BP325 belt pack Other industry standard single and dual channel PL intercom systems including those from Clear Com are also directly compatible To provide optimal signal matching and interface performance the nominal level of the Model 46 s 2 wire interfaces can be selected Using DIP switches accessible on the front panel the nominal levels can be selected to be either 10 or 14 dBu settings that should allow compatibility with virtually all party line systems For example for applications that use equipment from RTS the 10 dBu setting is appropriate For other equip ment such as that from Clear Com the 14 setting is correct Interface UAL 2 WIRE ANALOG AUDIO TO NALOG AUDIO INTERFACE INTERFACE 2 2WIRE 4MWIRE INTERFACE 1 MODEL 46 MADE IN USA v see user cuime e e i e e e v 9 PLINTERCOM LINEOUTCH2 LINEQUTCH1 LINEINCH2 LINEINCH 1 PLINTERCOM LINEOUTCH2 LINEOUTCH1 LINEINCH2 LINEINCH 1 23WIRE 43 Model 46 Back Panel Model 46 User Guide Studio Technologies Inc Issue 2 September 2007 Page 5 Model 46 Interface The Model 46 s 2 wire interfaces can correctly function with powered wet or unpowered dry intercom circuits Powered circuit
4. circuits The Model 46 can certainly be used in this fashion but adapter cables will have to be prepared These adapters will split the Model 46 s 2 wire PL intercom connectors into two 3 pin male XLR connectors one for each audio channel Pin 1 of the female 3 pin XLR intended to mate with the Model 46 will connect to pin 1 of both 3 pin male XLR connectors Pin 2 of the female XLR will go to pin 3 of the male XLR designated as channel 1 Pin 3 of the female XLR will go to pin 3 of the male XLR designated as channel 2 Refer to Figure 2 for details Us ing two adapter cables the Model 46 can be directly interconnected with four Clear Com intercom circuits However power for the connected devices must be provided by external power sources The Model 46 s ability to supply intercom power will not be utilized To 3 3 To Mode 46 Clear Com b entis 2 Circuit 1 onnector XLR F p ouem 3 To Clear Com 2 Circuit 2 1 XLR M Figure 2 Adapter cable wiring diagram Note It s critical that the correct con figuration settings be made when using the Model 46 s interfaces to support four independent intercom circuits Specifically the 2 wire power source configuration DIP switches must be set for external In addi tion the auto terminate disable DIP switch must be placed in its on up position Model 46 User Guide Studio Technologies Inc Refer to the Configuration and Advanced Configuration secti
5. either a power down power up sequence an auto null operation or a change to one of the level configuration DIP switches to take place While it is very unlikely that this type of ESD event would occur during normal field operation it is of concern for critical Model 46 applications To minimize the chance that the audio path could experience this problem a refresh routine was added to the Model 46 s operating software firmware To ensure that the ESD sensitive component always remains functioning correctly the software resends its operating instructions four times each second With this imple mentation the worst case scenario would result in an audio loss of 250 milliseconds or less in the event of an extreme ESD hit being experienced But nothing comes without a price and in this case the refresh routine adds a very slight audio tick to the 4 wire output and 2 wire party line signals During typical applications these refresh ticks will not be noticeable But there may be situa tions where any added audio artifact may simply not be acceptable To address this possible but highly unlikely case back panel DIP switch 3 can be used to disable the refresh routine When switch 3 is in its off down position the Model 46 operates in its standard fashion When switch 3 is in its on up position the refresh routine is disabled The Model 46 will continue to function normally with the exception that the f
6. few dB of their nomi nal values and as such could be support ed with a limited number of configurable choices In addition it was acknowledged that in this application analog audio cir cuitry was capable of providing excellent audio performance but that the required manual nulling process was operation ally taxing By adding digital control to the analog circuitry automatic nulling couldbe performed the best of both worlds The next step was to identify resources that would improve the installation process and make operation more reliable This led to the inclusion of multiple LED level meters allowing continuous monitoring of the input and output signals It also turned out that in many applications only a small number of user devices such as belt packs are Issue 2 September 2007 Page 9 Model 46 Interface typically connected to 2 wire party line circuits By adding DC power sources to the Model 46 s 2 wire interfaces the need for external intercom power supplies could often be eliminated The final step was to create a physical package that would provide significant re sources in a form that allowed simple and reliable integration with other equipment This was accomplished by including two 2 channel interfaces in a one rack space enclosure Using standard 3 pin XLR type audio connectors would enable rapid installation and troubleshooting And by making the Model 46 universally pow ered installatio
7. interaction problems will arise pin 1 on each of the line output connec tors is isolated from all Model 46 circuitry and ground points Floating pin 1 virtu ally eliminates the chance that a ground loop problem will occur 2 Wire Party Line Intercom Connections The Model 46 s 2 wire party line PL intercom interfaces are designed to di rectly connect with standard single and dual channel party line intercom devices Each of the two 2 channel PL interfaces is compatible with intercom circuits that have their own DC power sources Alternately the Model 46 can provide the DC power required by connected intercom user devices The internal 30 volt DC intercom power source is limited to 300 milliam peres of current This moderate amount of power requires that the type and num ber of connected user devices be selected appropriately For convenience the 2 wire PL intercom circuits can be connected to the Model 46 by way of four 3 pin male XLR type con nectors two are located on the back panel Issue 2 September 2007 Page 12 and two on the front They are organized in groups of two connectors per interface one on the back and one on the front They are wired in parallel multed and provide access to the identical signals Dual Channel Intercom Systems If compatibility with RTS TW systems is desired the mating connectors females should be wired so that common is on pin 1 DC with channel 1 audio is on
8. ohm terminations In both these cases the termination will be in error and will re sult in incorrect audio levels due a double termination condition To prevent this problem the auto termi nate function can be disabled When DIP switch 1 is in its off down position the auto terminate function is active When switch 1 is in its on up position the auto terminate function associated with each interface is disabled Repeating for clarity the auto terminate disable function applies to both interfaces 1 and 2 With the auto terminate function disabled the two 46 interfaces when set for external power will operate normally with the exception that pins 2 and 3 will never be terminated by the Model 46 s circuitry Model 46 User Guide Studio Technologies Inc Model 46 Interface The auto terminate disable function should be used only when absolutely necessary it s possible that a significant downside could be experienced With auto terminate disabled it s important that properly ter minated 2 wire party line intercom circuits be connected to pins 2 or 3 on the Model 46 s 2 wire PL connectors If they are not connected it s likely that audio oscilla tions noise and distortion will be gener ated in the Model 46 s 2 wire to 4 wire converter circuitry These audio artifacts will not cause any damage but will be sent out the 4 wire line output connectors Users of the 4 wire equipment may be less than pleased with what they h
9. pin 2 and channel 2 audio is on pin 3 This wiring scheme is correct whether the con nected devices are to be powered by an external source or by means of the Model 46 s internal power sources Single Channel Intercom Systems There are two ways of connecting to the Model 46 s 2 wire PL intercom connec tors when compatibility with Clear Com single channel intercom devices is de sired The most direct method is to pre pare the female XLR mating connector so that common is on pin 1 power is on pin 2 and audio is connected on pin 3 With this connection scenario only audio chan nel two associated with pin 3 of the Model 46 s 2 wire PL intercom interface connec tors will be utilized Pin 2 the Model 46 s audio channel one will only be used for connecting DC power to the connected devices While the audio resources pro vided by channel one will not be used the Model 46 can still be used to supply DC power on pin 2 As previously mentioned the maximum current draw on the 30 volt DC output is 300 milliamperes Alternative ly an external intercom power supply can support the connected devices In some single channel PL intercom sys tem applications it may be desirable to take full advantage of the two channels Model 46 User Guide Studio Technologies Inc Model 46 Interface associated with each Model 46 interface In these applications one might want to view the Model 46 as providing four 2 wire to 4 wire interface
10. specific applications a number of operat ing parameters must be configured These include the 2 wire party line power source the nominal 2 wire level and the nominal 4 wire level Three 4 position DIP type switch assemblies are used to establish the desired configuration One DIP switch assembly is associated with interface 1 a second is associated with interface 2 and third associated with advanced operat ing features that apply to both interfaces Configuration Interface 1 and 2 The DIP switch assemblies associated with interface 1 and 2 are accessible on the Model 46 s front panel They provide identi cal capability for their respective interfaces Refer to Figure 6 for a detailed view In this section the four switches associated with interface 1 will be covered in detail This information applies to interface 2 as well The four switches allow selection of the 2 wire party line power source the nominal level for the 2 wire party line channels and the nominal level of the 4 wire inputs and outputs INTERFACE 1 2WIRE MODE SWITCHES 2 WIRE POWER SOURCE STATUS 1 EXTERNALY INTERNALA T 2 WIRE NOMINAL LEVEL MODE AUTO 2 14 dBuY 10 dBua NULL 4 WIRE NOMINAL LEVEL 0123 4 8 34 OdBuYY 0 1 3 4 4 dBuAY 3 4 6 dBu 3 4 8 dBuA Figure 6 Detail of front panel showing four DIP switches 2 Wire Party Line Power Source DIP switch 1 is used to select whether or not the
11. 00 volts 0 4 amperes maximum 240 volts Dimensions Overall 19 0 inches wide 48 3 cm 1 72 inches high 4 4 cm 8 5 inches deep 21 6 cm Mounting one space in a standard 19 inch rack Weight 7 75 pounds 3 5 kg Specifications and information contained in this User Guide subject to change without notice Model 46 User Guide Studio Technologies Inc Model 46 Interface Appendix A Interfacing Telex RTS Matrix Intercom Systems with the Model 46 Interface ADAM Matrix Intercom System Analog Ports to Model 46 Interface 9 Pin D Sub Connector Female to Matrix Port Audio to Matrix 9 8 Audio from Matrix 7 3 When connecting to ADAM CS use only low profile receptacle gt 1 e g Tyco part no 747516 3 To Model 46 4 Wire Output XLR F To Model 46 4 Wire Input XLR M RVON I O Connections to Model 46 Interface 9 Pin D Sub Connector Female to Matrix Port 1 2 4 gt Audio to RVON I O 5 E 2 3 9 gt NC lt 1 8 gt 4 gt 2 Audio from RVON I O 7 We oo 3 3 gt NC gt 1 To Model 46 4 Wire Output XLR F To Model 46 4 Wire Input XLR M Model 46 User Guide Studio Technologies Inc Issue 2 September 2007 Page 29 Appendix B Model 46 Interfacing Riedel amp Artist Matrix Intercom System Analog Ports with the Model 46 Interface 8
12. 1 2 CH2 2 STUDIO TECHNOLOGIES INC MODEL 46 DUAL 2 WIRE ANALOG AUDIO TO 4 WIRE ANALOG AUDIO INTERFACE BLOCK DIAGRAM DRAWING NO DATE PAGE 51255 01 10 07 02 or 02
13. AND PASS FILTER 2 2 148 33 1 gt m 25 1408 33 102 4 E 100Hz BkHz 2 ON OFF ON OFF TO MCU 3 LOCATED CONTROL CONTROL A D INPUT 3 FRONT PANEL FROM MCU FROM MCU L1 2 WIRE 200 OHM INTERCOM PL INTERCOM CIRCUIT LEVEL BI LATERAL IMPEDANCE POWER 30V 300mA MAX CONTROL BUFKER CURRENT SOURCE GENERATOR SOURCE 14 10dBu XLR M AW e gt 2 1 gt LOCATED ON 3 BACK PANEL DATA TONE1 1 FROM MCU Y TO LEVEL DETECTOR CHI 1 CONTROL BUFFER DIGITALLY 600 600 4 WIRE OUTPUT CONTROLLED 2 INTERFACE 1 4 AERE 3 CHANNEL 1 0 4 6 84 DATA 1 V FROM 1 4 LEVEL METER TG FROM nee 26 4 WIRE 648 INPUT 26 1248 26 1848 2Y amp 6098 LEVEL METER L d4 og 26 4 WIRE 6d8 OUTPUT 1208 26 1848 ON OFF TO MCU CONTROL 3 A D INPUT FROM MCU 200 OHM LEVEL BE LATERAE IMPEDANCE CONTROL BUFFER CURRENT SOURCE GENERATOR W TONE2 1 FROM MCU TO LEVEL Eve DETECTOR CH2 1 CONTROL BUFFER DI ALLY 500 600 4 WIRE OUTPUT 2 INTERFACE 1 1 HYBRID E m CHA
14. Model 46 Interface User Guide Issue 2 September 2007 This User Guide is applicable for serial numbers M46 00180 and later and units upgraded with software version 1 3 and higher Copyright 2007 by Studio Technologies Inc all rights reserved www studio tech com 50110 0907 Issue 2 This page intentionally left blank Model 46 Interface Table of Contents rere eer ryt rr 5 VRS VAN 10 AOU IN UN ass 16 Advanced Configuration 18 E 20 Advanced 25 Technical Notas sociedad eno 26 lere secure 28 Appendix A Interfacing with Telex RTS Matrix Intercom Systems tenentes 29 Appendix B Interfacing with Riedel Artist Matrix Intercom 30 Appendix C Interfacing with Clear Com Matrix Intercom 8 31 Block Diagram Model 46 User Guide Issue 2 September 2007 Studio Technologies Inc Page 3 Model 46 Interface This page intentionally left blank Issue 2 September 2007 Model 46 User Guide Page 4 Studio Technologies Inc Model 46 Interface Introduction The Model 46 is designed to interface 2 w
15. Model 46 provides DC power to pin 2 of connectors associated with the 2 wire party line intercom channels Two 3 pin male XLR type connectors one located on the Model 46 s front panel and one on the back panel are used to interconnect the Model 46 with the inter com user devices When switch 1 is in its off down position the Model 46 will not provide DC power This switch setting is appropriate when an external intercom Issue 2 September 2007 Page 16 Model 46 User Guide Studio Technologies Inc Model 46 Interface power supply is providing power to the intercom circuit In addition to power it s expected that the external power supply will also provide the required 200 ohm ter minating impedance to both pins 2 and 3 When switch 1 is in its on up position the Model 46 will provide a 30 volt 300 mil liamperes maximum source of DC power to pin 2 of the 2 wire PL intercom connec tors The Model 46 will also provide 200 ohm terminating impedances for both pin 2 and pin 3 of the party line connectors The DC power and termination capabili ties allow direct powering of dual chan nel intercom belt packs such as the RTS BP325 In addition listen only belt packs such as the Model 34 from Studio Tech nologies Inc can be directly connected There s also no problem connecting single channel intercom belt packs or user stations 2 Wire Nominal Audio Level DIP switch 2 allows adjustment of the nominal audio
16. NNEL 2 DATA nc gt 1 0 4 6 8dBu FROM MCU Y XLR M 43668 LEVEL METER lt 6 FROM 148 26 4 WIRE 6d8 INPUT 26 M 128 26 2Y amp 68 LEVEL METER 6 H 26 4 WIRE 6d8 OUTPUT 26 d4 1248 A M46BD B 188 STUDIO TECHNOLOGIES INC MODEL 46 DUAL 2 WIRE ANALOG AUDIO TO 4 WIRE ANALOG AUDIO INTERFACE BLOCK DIAGRAM DRAWING NO DATE PAGE 31235 01 10 07 01 or 02 EEPROM MEMORY MICRO CONTROLLER INTEGRATED CIRCUIT MCU AW 1 sAn x REMOTE lt AW CONTROL 2 p INPUTS t W 3 7h CONNECTOR LOCATED ON PRINTED CIRCUIT BOARD ASSEMBLY AC MAINS INPUT 5 AUTO NULL INTERFACE 1 FUR 9 9 AUTO NULL INTERFACE 2 re CONFIGURATION SWITCHES 1 e TYPICAL OF 12 STATUS LEDS TYPICAL OF 9 DATA SIGNALS TO DEVICES A D INPUTS SINE WAVE DUAL TONE 4X1 GENERATOR SWITCH FULL WAVE LEVEL DETECTOR 100 240 50 60Hz OPERATION lt IEC 320 C14 INLET FUSE POWER SUPPLY POWER 9 5v SUPPLY TONE1 1 TONE2 1 TONE1 2 TONE2 2 CHI 1 CH2 1 CH
17. a tion impedances must be provided by the connected circuits If these are not pres ent one should expect the hybrid circuits to generate a very impolite noise This condition caused by the 2 wire output circuitry being in an unloaded state will not damage the Model 46 s circuitry But errors in cable patching a disconnected cable or other real world issues can lead users listening to signals that originate in the Model 46 s 4 wire outputs from being presented with a rude surprise In conclusion it s important that technical personnel working with the Model 46 be informed when the auto termination func tion has been disabled They will then be aware of the potential noise issues and be ready to make corrections should a prob lem arise Issue 2 September 2007 Page 25 Model 46 Interface Factory Test Mode Back panel DIP switch 4 allows a factory test mode to be enabled During normal operation switch 4 should remain in its off down position When switch 4 is in its on up position factory mode is active En abling this mode will result in the following operating condition during an auto null sequence the associated 4 wire output channel will remain active This will allow the tones associated with the nulling pro cess to be present on the 4 wire output While not appropriate during actual Model 46 use it is interesting to hear the null ing process take place But unless direct ed by factory personne
18. allows a single tap of the button to initiate nulling of both hybrid circuits When DIP switch 2 is in its on up posi tion the independent auto null mode is selected This would be appropriate for applications in which the two audio paths associated with each interface are used with independent party line intercom circuits This situation might arise when two Clear Com single channel intercom circuits are connected to one of the Model 46 s dual channel interfaces The hybrid circuit associated with each channel can be auto nulled as desired Another exam ple would be in an RTS TW series applica tion that uses source assignment panels The SAP panels would be used to route multiple intercom channels to various sets of user devices as desired In this case the two channels associated with each Model 46 interface will often end up not routed to the same user device indepen dent auto nulling is certainly desired Refresh Disable While testing the Model 46 as part of the development process it was found that in cases of extreme ESD electro static discharge or static an integrated circuit in the audio signal path could latch up This would result in the audio signal no Issue 2 September 2007 Page 19 Model 46 Interface longer passing through this component and on to the 4 wire audio output When ever this situation arose the component was not damaged but restoring the flow of audio required
19. ample would be a Model 46 interface configured for 8 dBu operation and a 12 dB LED is lit This indicates that a signal with audio level 4 dBu is present on its associated output Each level meter contains four green LEDs and one yellow LED The four green LEDs indicate signal levels at or below the configured nominal level The top LED is yellow in color and indicates a signal that is 6 dB or greater than the nominal level An audio signal that causes the yellow LED to light doesn t necessarily indicate Model 46 User Guide Studio Technologies Inc an excessive level condition but it does provide a warning that at some stage reducing the signal level may be prudent Normal operation with normal signal levels should find the meters lighting near their 0 dB point Signal peaks may cause the yellow LEDs to flash But a yellow LED that lights fully during normal operation will typically indicate a signal level or configu ration problem If the from 4 wire meters display consis tency lower or higher levels than their 0 dB points it s possible that a configuration is sue exists One potential problem is incor rectly set 4 wire nominal audio level DIP switches for one or both of the Model 46 s interfaces If the nominal level is set too low then sufficient audio headroom might not be available It can also result in ex cessively high audio signals being sent to 2 wire party line circuits Setting the nomi nal level f
20. ating conditions Specifically 200 ohm impedances are automatically applied to both pins 2 and 3 of a Model 46 2 wire party line interface when that interface is configured for external power and no ex ternal source of intercom power is detect ed on pins 2 or 3 This function is directly compatible with RTS TW series intercom applications in which the three conductors of a cable support both DC power and two channels of audio It s also compatible in situations where all three conductors of a Clear Com single channel intercom circuit Issue 2 September 2007 Page 18 are connected to the Model 46 In this lat ter case only one of the Model 46 s audio channels will be used There may be situations where it s nec essary for the two channels associated with each Model 46 interface be used with separate 2 wire party line circuits An example of this might be where two loops of single channel belt packs such as units from Clear Com need to be connected Adapter cables as shown in Figure 2 would be used In this case the intercom circuit s DC power will not be connected to the Model 46 but only to the user devices In this scenario a DC volt age won t be present on pin 2 or pin 3 Another example of this might be where adapter boxes with DC blocking are used to interconnect intercom circuits with the Model 46 In both these cases a DC volt age won t be present on either pin 2 or 3 and the Model 46 will automatically apply 200
21. ation of the auto null process flashing when the auto null process for its respective chan nel is active INTERFACE 1 4 WIRE CH 1 2 WIRE POWER 4 status PIN3 MODE AUTO 01234 Figure 8 Detail of front panel showing auto null section Issue 2 September 2007 Page 24 An actual auto null sequence starts by muting the 4 wire input and output signal paths associated with the specific channel to be nulled Then a short period of 24 kHz signal is sent out the 2 wire PL intercom interface channel This will turn off micro phones on those connected user devices that are compatible with the RTS TW series mic kill protocol The actual auto nulling process will next be performed A series of tones will be sent out the 2 wire interface Other Model 46 circuitry un der software control will rapidly perform adjustments to achieve the best null pos sible After the adjustments are made the results are stored in non volatile memory Once the process has completed the 4 wire input and output paths are again activated Advanced configuration DIP switch 2 located on the back panel allows an independent auto null button mode to be selected If switch 2 is in its on up position the front panel pushbuttons will function in quite a different manner In the independent mode a single tap to a switch will cause channel 1 to auto null Two taps will cause channel 2 to auto null By observing the op
22. cle of 6 seconds on 5 seconds for start up and one second for detection and 5 seconds off As a diagnostic aid the 2 wire power status LED associated with pin 3 remains active in the internal power mode When ever DC in excess of approximately 18 volts is present on pin 3 the LED will light This condition will normally never exist but could prove useful in special circumstances Issue 2 September 2007 Page 23 Model 46 Interface Auto Null Each of the Model 46 s dual channel inter faces has circuitry to automatically null the two 2 wire to 4 wire interfaces Normally this process is performed at the time of initial Model 46 configuration but there s no reason why auto nulling can t be initi ated anytime one desires The only time that auto null must be performed is if con ditions have changed vis a vis the inter com user devices and wiring connected to a Model 46 2 wire PL interface connector Even a slight change to an intercom cir cuit such as adding or removing a section of cable is sufficient to require that the auto null process be performed Two buttons one associated with each interface are provided to activate the auto null process Refer to Figure 8 fora detailed view To initiate auto null simply requires pressing and releasing ping a button The process begins by nulling channel one of an interface and when completed moves on to channel two Two LEDs provide a visual indic
23. ctable Mic Kill Signal square wave 24 kHz 1 Internal Power Source 30 volts DC nominal 300 milliamperes maximum Hybrids 4 2 per interface Topology 3 section analog circuitry compensates for resistive inductive and capacitive 2 wire party line loads Nulling Method automatic upon user initiation processor implements digital control of analog cir cuitry null settings stored in non volatile memory Nulling Line Impedance Range 120 350 ohms Nulling Cable Length Range 0 3500 feet typical Trans Hybrid Loss 240 dB typical at 800 Hz Issue 2 September 2007 Page 28 4 Wire Inputs 4 2 per interface Type transformer coupled capacitor isolated Impedance 13 k ohms Nominal Level 0 4 6 or 8 dBu selectable in tandem with nominal output level Maximum Level 22 dBu 4 Wire Outputs 4 2 per interface Type transformer coupled capacitor isolated Impedance 50 ohms nominal Nominal Level 0 4 6 or 8 dBu selectable in tandem with nominal input level Maximum Level 20 dBu into 2 ohms Meters 8 Function displays level of 4 wire inputs and outputs Type 5 segment LED modified VU ballistics Remote Control Inputs 3 Type optically coupled Input 3 32 volts DC 2 milliamperes minimum for operation 20 milliamperes maximum Functions auto null interface 1 auto null interface 2 and mic kill AC Mains Requirement 100 240 volts 715 4 1096 50 60 Hz 0 7 amperes maximum 8 1
24. ear Auto Null Button Operation One pushbutton switch is associated with each of the Model 46 s two interface circuits An advanced configuration pa rameter allows selection of the button s operation The choices are dual auto null mode and independent auto null mode When dual auto null mode is selected a single tap press and release of one of the two front panel pushbutton switches initiates a routine that begins with chan nel 1 s auto null sequence taking place followed immediately by channel 2 s auto null sequence being performed Note that the mode selected for auto null button op eration will also apply to the remote auto null inputs The independent auto null mode allows the auto null function to be initiated for each channel as desired A single tap will start the auto null routine for channel 1 Two taps will start the routine for channel 2 When DIP switch 2 is in its off down posi tion the dual auto null mode is selected Model 46 User Guide Studio Technologies Inc This is provided specifically for cases where the Model 46 s 2 wire party line interfaces will be used with dual channel intercom user devices As an example the RTS TW series provides two independent audio channels as well as power over a single 3 conductor cable In a case such as this it s useful for both of the hybrid circuits associated with an interface to be auto nulled at approximately the same time The dual auto null mode
25. eration of the two auto null status LEDs it will become readily apparent which of the button modes has been selected If possible prior to performing an auto null it s polite to warn all personnel who are actively using the connected intercom devices The tones sent to the 2 wire inter com circuit during the nulling process are not excessively loud or obnoxious but most users might want to remove their headsets during the process In addition to warning users it might be a good time to ask them to mute any Model 46 User Guide Studio Technologies Inc Model 46 Interface active microphones While the automatic mic kill signal will apply to many user devices it may not apply to all Muting microphones is significant as obtaining a deep null requires that no extraneous signals be present on the intercom circuit Advanced Operation The Model 46 allows several of the operat ing parameters to be configured to meet the needs of specific applications The following paragraphs provide details about the auto terminate disable and factory test modes Auto Terminate Disable As previously discussed in this user guide the auto terminate function can come into play when a 2 wire interface is configured for external power Using a combination of hardware and software pins 2 and 3 of each 2 wire PL intercom connector are monitored for the presence of DC voltage If a level of greater than approximately 18 volts
26. ften found in broadcast applications The parameters obtained during the nulling process are stored in non volatile memory mains power interruptions won t require the auto nulling function to again be performed A sine wave audio tone is generated for use during the auto nulling process The frequency is software controlled to maxi mize the ability of the hybrid circuits to reach a deep null In addition at the beginning of each auto null sequence a short period of 24 kHz tone is sent to the associated 2 wire party line interface This serves as a microphone disable mic kill signal for user devices such as the RTS BP325 By automatically disabling open microphones the auto nulling process can achieve better performance 4 Wire Interfaces Associated with the 4 wire portion of the Model 46 s interfaces are analog line level inputs and outputs These are intended to interconnect with a variety of 4 wire de vices including matrix intercom systems audio over fiber transmission systems and other specialized audio equipment The input and output circuitry is transform er coupled to minimize the chance of hum noise or ground loop issues A key characteristic of the Model 46 s de sign is the ability to select the 4 wire input and output nominal levels This helps to ensure compatibility with virtually all audio equipment Front panel accessible DIP switches allow the nominal levels to be configured fro
27. h the connected nominal level The switches work in tandem to control both the input and output nominal levels Audio sources are connected to the line inputs by way of 3 pin female XLR type connectors which are located on the unit s back panel Refer to Figure 1 for a detailed view Note that pin 1 of these connectors is internally connected to the Model 46 s earth chassis ground point Prepare the mating connectors males so that pin 2 is signal high or hot pin 3 is low or cold and pin 1 is shield If connecting a source in this manner results in hum or noise it s possible that remov ing the shield connection from pin 1 can eliminate the issue floating pin 1 will remove a potential ground current path from the Model 46 s earth chassis ground point through the shield of a cable Also if a hum or noise issue does arise be certain to confirm that unless absolutely neces sary the mating connector s shell isn t connected to the cables shield or pin 1 Termination of this fourth pin of a 3 pin XLR connector is often the cause of seem ingly inexplicable noise issues With an unbalanced source connect pin 2 to signal high or hot and both pins 1 and 3 to shield If connecting an unbalanced source in this manner results in hum or noise connect pin 2 to high or hot and pin 3 to shield leave pin 1 unterminated 4 Wire Line Outputs Each of the Model 46 s two interfaces prov
28. h a detach able mains cord set For units shipped to North America and Japan a cord is sup plied that has a North American NEMA 15L standard plug on one end and an IEC 320 C13 type connector on the other Units bound for other destinations require that the appropriate cord set be obtained The wire colors in the mains cord should conform to the internationally recognized color code and should be terminated according to the following chart MAINS INPUT e C 100 240V 50 60Hz 0 7A MAX 100V 0 4A MAX 240V A sE USER GUIDE Figure 5 Detail of back panel showing AC mains power connector Issue 2 September 2007 Page 15 Model 46 Interface Connection Wire Color Neutral N Light Blue Line L Brown Earth Ground E Green Yellow Safety Warning The Model 46 does not contain an AC mains disconnect switch As such the AC mains cord plug serves as the disconnection de vice Safety considerations require that the plug and associated inlet be easily accessible to allow rapid disconnec tion of AC mains power should it prove necessary As soon as AC mains power is applied the Model 46 will begin its power up sequence As a boot up indication the power LED and each of the status LEDs will momentarily light After the sequence has completed the power LED will again light and remain lit The unit is now fully functional Configuration For the Model 46 to support the needs of
29. hat uses two sets of three BP 325 belt packs can easily be supported Each interface s 30 volt DC Issue 2 September 2007 Page 6 intercom power source ensures that sys tems requiring long intercom cable runs will function correctly The circuitry s out put regulation is such that little change in the output voltage will occur over its entire rated output current Also the unique de sign of the power supply circuitry virtually eliminates the noise and hiss associated with typical intercom power supply perfor mance Under software control the output of the DC power supplies are monitored for over current and short circuit condi tions This allows protection shut down of the output DC as well as providing an alert by way of a visual indicator Analog Hybrids with Auto Nulling A key reason that the Model 46 s inter faces achieve excellent audio performance is the design of the 2 wire to 4 wire hybrid circuits They provide low noise and dis tortion good frequency response and high return loss nulling even when presented with a wide range of 2 wire conditions Unlike telephone line POTS oriented DSP based hybrid circuits the Model 46 s analog circuitry provides ex tended frequency response With a pass band of 100 Hz on the low end and 8 kHz on the high end natural sounding voice signals can be sent to and received from the 2 wire party line circuits A hybrid s ability to isolate the transmit
30. ides two analog line level audio out puts These outputs are intended to be connected to inputs on the devices asso ciated with the 4 wire audio signals The outputs are capacitor coupled transform er balanced with a nominal level of 0 4 6 or 8 dBu As previously mentioned the 4 wire nominal level configuration switches located on the Model 46 s front panel control the level of both the line outputs and the line inputs The 4 wire line WARNING 30 VOLTS DC MAY BE e WIRE PRESENT ON PIN 2 OF 2 WIRE CONNECTORS ADVANCED MODE acm a e EL M ET ERE MEE UR LEER 4 WIRE ani ue PL LINE OUT 2 LINE OUT 1 LINE IN 2 LINE IN 1 Figure 1 Detail of back panel showing line inputs and outputs Model 46 User Guide Studio Technologies Inc Issue 2 September 2007 Page 11 Model 46 Interface outputs are capable of driving inputs that have impedances as low as 600 ohms however connecting to loads of 2 k ohms or greater is preferred The line outputs are connected by way of 3 pin male XLR type connectors which are located on the Model 46 s back panel Refer to Figure 1 for a detailed view The mating connectors females should be prepared so that signal high or hot is expected on pin 2 Signal low or cold should be expected on pin 3 The cables shields can be connected to pin 1 How ever in order to minimize the chance that ground
31. igure up to three of these units can be connected to each Model 46 interface Newer versions of the BP325 use surface Model 46 User Guide Studio Technologies Inc mount component technology and have a lower maximum current draw of 65 mil liamperes Four of these modern BP325 units can easily be supported The Model 46 s intercom power supply circuits operate under software control This allows detection of fault conditions and protection of both the Model 46 s circuitry and connected intercom user devices Upon initial Model 46 power up no monitoring of the intercom power output takes place for a period of five seconds This allows the Model 46 s circuitry and the connected intercom user devices to stabilize The LED associated with pin 2 will light to indicate that the output is active After this initial 5 second period monitoring becomes active A fault condition is detected if the power on pin 2 falls below 24 volts for a continuous one second interval The hardware and soft ware responds to this condition by turning off the power source to pin 2 and flashing the pin 2 LED as a warning After a five second down interval the output re turns to the same condition as upon initial power up power is again applied to pin 2 the pin 2 status LED will light and moni toring won t begin for another five sec onds A full short circuit condition applied to the Model 46 s 2 wire connectors will result in a continuous cy
32. ire full duplex party line intercom cir cuits with 4 wire audio circuits associated with matrix intercom systems Other spe cialized audio system interfacing applica tions can also be supported The Model 46 provides two independent full featured 2 channel interfaces Each interface con tains two hybrid circuits which include automatic nulling capability The analog Circuitry under software control provides excellent audio quality and high return loss The interfaces are compatible with powered and unpowered 2 wire party line circuits They are capable of supplying DC power allowing direct operation of devices such as user belt packs Configuration set tings allow the 2 wire and 4 wire interface Circuitry to be compatible with a range of nominal signal levels Audio level me ters provide user confirmation of system performance during setup and operation Applications for the Model 46 include tele vision sports and special event broadcast ing theme park and theater installations corporate events and industrial testing environments Standard audio connectors are used for all input and output signals The Model 46 mounts in one space of a standard 19 inch rack enclosure and requires 100 240 volts 50 60 Hz for operation 2 Wire Interfaces The Model 46 s 2 wire interfaces are optimized for direct connection with dual channel party line PL intercom circuits In addition single channel party line intercom circuits can
33. ith equipment manufactured in Europe such as the digital matrix intercom systems from Riedel The 8 dBu setting is provided specifically when interconnect ing the Model 46 with audio signals asso ciated with an RTS ADAM series of matrix intercom system This includes the related RVON I O unit When DIP switches 3 and 4 are in their off down position the nominal level is set for 0 dBu When switch 3 is on up and switch 4 is off down the nominal level is 4 dBu When switch 3 is off down and switch 4 is on up the nomi nal level is 6 dBu When both switches 3 and 4 are in their on up position the nominal level is configured for 8 dBu Issue 2 September 2007 Page 17 Model 46 Interface Advanced Configuration Four DIP switches are provided on the Model 46 s back panel They allow the two interfaces to be configured for several ad vanced operating modes Refer to Figure 7 for a detailed view of these DIP switches The available modes include auto termi nate disable auto null button operation refresh disable and factory test WARNING 30 VOLTS DC MAY BE 2 WIRE PRESENT ON PIN 2 OF 2 WIRE CONNECTORS ADVANCED MODE 01234 PL INTERCOM Figure 7 Detail of back panel showing the Advanced Mode DIP switches Auto Terminate Disable The auto terminate function is designed to ensure that each 2 wire to 4 wire interface circuit remains stable under most oper
34. l switch 4 should remain in its off down position Interface 1 LED Section Major Release Number 4 3 O2 e i Technical Notes Software Version Display A special Model 46 power up sequence allows the unit s software version number to be displayed This is useful when work ing with factory personnel on application support and troubleshooting situations The four status LEDs associated with interface 1 are used to display the major release number with a range of 1 through 4 The four status LEDs associated with interface 2 are used to display the release sub number which again ranges from 1 through 4 Refer to Figure 9 for a detailed view of the status LEDs and the corre sponding software version numbering scheme The Model 46 s initial software release is version 1 1 which is represented by the bottom LEDs of each status column being lit Interface 2 LED Section Release Sub Number 40 3 20 1 4 WIRE CH 1 4 WIRE CH 2 2 WIRE P POWER 4 x x e STATUS e 6 9 Qo TO INTERFAGE 2 4 WIRE CH 1 2 WIRE 6 POWER STATUS MODE AUTO NULL PL INTERCOM Figure 9 Detail of front panel showing the status LEDs that display the software version In this example the software version is 1 3 Issue 2 September 2007 Page 26 Model 46 User Guide Studio Technologies Inc Model 46 Interface To display the Model 46 s software versio
35. level for the two 2 wire party line channels associated with inter face 1 When the switch is in its off down position the nominal level is 14 dBu This level is compatible with intercom belt packs from manufacturers such as Clear Com When the switch is in its on up position the nominal level is 10 dBu This setting is appropriate when belt packs from RTS such as the BP325 or listen only talent amplifier units from Studio Technologies Inc are connected For best Model 46 performance it s important that the 2 wire nominal level selection be made correctly Model 46 User Guide Studio Technologies Inc 4 Wire Nominal Audio Level DIP switches 3 and 4 are used to config ure the nominal level of the input and out put circuitry associated with interface 1 s two 4 wire input and output connections Four level settings are available 0 4 6 and 8 dBu Prior to setting these DIP switches it s important to determine the nominal audio level of the equipment con nected to the Model 46 s 4 wire input and outputs This may take a little investigation but is important for obtaining the best pos sible Model 46 performance The 0 dBu setting is provided specifically for use when a Model 46 is interconnected with a Clear Com matrix intercom system The 4 dBu setting is appropriate when standard audio lines with 4 nominal levels are interconnected The 6 dBu setting can be appropriate when intercon necting w
36. loop that s best left to the brave of heart Model 72 Interface And now for a shameless product plug Studio Technologies Inc manufactures a nifty product called the Model 72 Level Meter Interface A compact standalone unit it can prove very useful when setting up maintaining and troubleshooting inter com circuits It will give a direct indication of signal levels at any point in a single or dual channel intercom circuit Check it out Issue 2 September 2007 Page 27 Model 46 Interface Specifications General Audio Frequency Response 2 dB 100 Hz to 8 kHz Distortion THD N lt 0 5 measured at 1 kHz 4 wire input to 2 wire interface pin 2 Signal to Noise Ratio gt 55 dB measured at 1 kHz 4 wire input to 2 wire interface pin 2 Connectors Inputs from 4 Wire 3 pin female XLR type Outputs to 4 Wire 3 pin male XLR type 2 Wire Party Line Intercom 3 pin male XLR type Remote Control 10 pin header requires optional 10 pin ribbon connector assembly AC Mains 3 blade IEC 320 C14 type mates with IEC 320 C13 2 Wire Party Line Intercom Interfaces 2 Type 2 channel party line PL unbalanced pin 1 common pin 2 DC with channel 1 audio pin 3 channel 2 audio Compatibility single and dual channel intercom systems such as from Telex RTS and Clear Com amp Impedance External Power Mode gt 10 ohms Impedance Internal Power Mode 200 ohms Nominal Level 10 or 14 dBu sele
37. m among four choices 0 4 6 or 8 dBu The 0 dBu setting was specifically provided for compatibility with Clear Com matrix intercom systems The 4 dBu setting allows standard audio signals to be directly connected Digital matrix intercom systems from Riedel can be effectively connected using the 6 dBu setting And the 8 dBu setting allows proper level matching with the popular ADAM series of matrix intercom systems from Telex RTS This setting also applies to the related RVON I O VoIP product The Model 46 contains eight 5 segment LED level meters Four of the meters are provided for each interface with two displaying the level of the signal being received from the 4 wire source and two displaying the level being sent to the 4 wire output During installation and setup the meters are invaluable in help ing to confirm that the nominal level DIP switch settings have been properly made During normal operation the meters offer rapid confirmation of audio signal flow in Issue 2 September 2007 Model 46 User Guide Studio Technologies Inc Page 7 Model 46 Interface and out of the unit Additional LED status indicators are also provided offering a clear view of the 2 wire DC power and auto null functions Pro Audio Quality The Model 46 s audio circuitry was de signed in the spirit of professional audio equipment rather than that found in typical party line intercom gear High performance co
38. mponents are used throughout providing low distortion low noise and high head room Using passive and active filters the frequency response is limited to approxi mately 100 Hz to 8 kHz This range was se lected to provide excellent performance for human speech while maximizing the ability of the hybrids to create substantial nulls When the Model 46 s internal DC power sources are selected to provide 2 wire party line intercom power enhanced audio performance can also be expected The quality of the DC supply circuits is excellent with very little noise hum or hiss being added to the 2 wire connections In addi tion the impedance characteristics of each interface s DC powered wet channels was tailored to be essentially identical to that of the unpowered dry channel This unique situation allows the automatic null ing circuitry to provide excellent consistent results for both the powered and unpow ered channels Attention to detail is a hallmark of the Model 46 s design For example during the brief auto nulling process an interface channel s 4 wire input and output signal is muted preventing unwanted audio from reaching the connected equipment Associated with the 2 wire interfaces is circuitry that under software control applies 200 ohm termi nating impedances to the 2 wire party line Issue 2 September 2007 Page 8 circuits This along with other circuitry that monitors DC v
39. n is very simple From the powered down state press and hold the auto null button associated with interface 1 Apply mains power while continuing to press the but ton The normal power up sequence will not occur but instead one LED will be lit in the column associated with interface 1 and one LED will be lit in the column associated with interface 2 As previously described these two LEDs represent the unit s current software version While the software version number is being displayed the LED level meters will likely display random readings This is not a problem and can simply be ignored After the software version number has been read the auto null button can be released At this time the unit will begin its normal power up sequence Note that while it s easy to determine which software version is loaded into the Model 46 a trip back to the factory is required to update it The 8 bit microcontroller that provides the unit s logic horsepower also includes internal FLASH memory This non volatile memory is used to store the operat ing software firmware Re programming this memory requires using a specialized programming unit While not outrageous in price it still costs in the range of US 500 The programmer uses a ribbon cable and socket to interface with a 6 pin head er on the Model 46 s printed circuit board And as you would guess once connected reprogramming takes only a matter of sec onds But unfortu
40. n in any locale could be directly supported Installation In this section you will be installing and interconnecting the Model 46 The one rack space unit will be mounted in an equipment rack Audio input audio out put and party line intercom connections will be made by way of 3 pin XLR type connectors AC mains power will be con nected by means of a detachable cord set that is compatible with the Model 46 s 3 pin IEC 320 C14 type inlet connector System Components The shipping carton contains the Model 46 Interface and associated user guide Units destined for North America and Japan also include an AC mains cord Your dealer or distributor should provide an AC mains cord for other destinations Locating the Model 46 The Model 46 s mounting location will dic tate the length of the cable runs needed to Issue 2 September 2007 Page 10 link the unit with the connected devices This is really only a factor in relation to the 2 wire party line intercom circuits These Circuits carry unbalanced audio which can be susceptible to interference and crosstalk issues Intercom circuits also carry DC power which may make resistive losses come into the picture In general shorter intercom cable lengths will as sure more reliable and consistent system performance Another location criterion is access to the Model 46 s front panel An optimal location will allow convenient use of the auto null push buttons and easy observa
41. nately the programmer is not something that would be found in a typical field shop or repair facility Not a TW 12B Replacement The Model 46 will provide a high level of performance over its range of intended Model 46 User Guide Studio Technologies Inc tasks But it s not intended to act as a universal 2 wire to 2 wire interface such as is provided by the venerable Clear Com TW 12B The Model 46 s 2 wire inter faces are not isolated from each other they share the Model 46 s internal power supply s common connection The power supply common point is DC isolated from chassis and earth ground Specifically pin 1 on the XLR connector associated with interface 1 s 2 wire party line inter face is electrically connected to the pin 1 connection on interface 2 This is due to the fact that both 2 wire party line inter faces are capable of supplying DC power to connected devices They also use the resources of a single set of logic circuitry And as such they each require access to the Model 46 s common power supply circuitry There s no doubt that a Model 46 could be used to create a 2 wire to 2 wire party line bridge by cross linking the 4 wire inputs and outputs using standard XLR type audio cables But it s likely that a significant ground loop would be cre ated through pin 1 of each of the Model 46 s 2 wire interfaces While it s possible to use a set of special isolation transform ers to eliminate the ground
42. nnected user devices or wiring associated with the 2 wire party line intercom be changed Upon power up the Model 46 will go through a short initial ization sequence before normal operation will begin The power and status LEDs will each light sequentially and upon Model 46 User Guide Studio Technologies Inc Model 46 Interface completion the power LED will light steadily The settings for the four hybrid Circuits are stored in non volatile memory and will be recalled during the power up process Level Meters The Model 46 contains eight 5 segment LED level meters These meters are pro vided as a support aid during installation configuration operation and trouble shooting The meters represent the sig nals coming in from and going out to the 4 wire connections The meters are organized in four groups each represent ing one input and one output They are calibrated to reflect the level in dB rela tive to the configured nominal operating level This is similar to the way in which now legacy VU meters functioned As an example let s take the situation where the nominal operating level of an interface is configured for 4 dBu and an output to 4 wire LED labeled 0 is lit For this example the level on the 2 wire PL circuit is just large enough to light the 0 LED This indicates that a signal with an approx imate level of 4 dBu is present on the as sociated 4 wire output connector Another ex
43. o be connected Depending on the setting of the configuration DIP switches either an external intercom power source or the Model 46 s internal 2 wire power source has been designated for supporting the connected user devices External Power Source When set for an external 2 wire power source the Model 46 will not provide power on pin 2 of the 2 wire connectors nor will the Model 46 use any power from a connected intercom circuit As expected audio signals will be sent from and re ceived by each interface s two audio cir cuits In this mode of operation the Model 46 acts as a typical user station on the connected intercom circuit As a connection confirmation hardware and software in the Model 46 monitors pins 2 and 3 of the 2 wire PL intercom connectors for the presence of DC volt age A level greater than approximately 18 volts DC on pin 2 will cause the status LED labeled pin 2 to light A level greater than 18 volts DC on pin 3 will cause the pin 3 status LED to light The author is aware that user intercom devices almost always draw power from pin 2 rather than pin 3 However in many broadcast applications power is provided on all intercom paths so that flexible chan nel assignments can be made In the Model 46 User Guide Studio Technologies Inc Model 46 Interface external 2 wire power mode the Model 46 is simply an observer whether intercom power is present on pin 2 pin 3 or both pins 2 and 3 is not
44. o be remotely controlled These features include remote auto nulling for each inter face and remote mic kill activation Model 46 User Guide Studio Technologies Inc Model 46 Interface Simple Installation The Model 46 uses standard 3 pin XLR type connectors to allow convenient inter connection in most broadcast and general audio environments For flexibility access to the 2 wire party line intercom interfaces can be made using the connectors pro vided on both the front and back panels In permanent installations the back panel connectors will typically be utilized In other settings such as field television pro duction front panel access allows inter com belt packs to be rapidly connected without requiring access to the inside of a rack enclosure or necessitating the use of a secondary input output I O panel The Model 46 is housed in a rugged steel enclosure that is designed to be road tough It mounts in one space of a stan dard 19 inch rack enclosure The mains input source can range from 100 to 240 volts 50 60 Hz allowing direct operation virtually anywhere in the world A switch mode power supply contained within the Model 46 s enclosure provides conver sion of the mains input power into the DC voltage required by the intercom power supply circuits Also contained within the unit is a DC to DC converter that creates the voltages required by the analog and digital circuitry These efficient po
45. oltages present on the 2 wire circuits ensures that audio instabil ity associated with unterminated circuits will rarely occur As previously mentioned the Model 46 s 2 wire DC power sources offer a unique level of performance Their ability to deliver power while maintaining audio quality is simply unmatched Special Applications While the Model 46 is designed to directly integrate into typical applications it s ready to support the one in a million situations too To accomplish this DIP switches accessible on the back panel allow some of the automatic features to be disabled For example one switch allows the auto terminate feature to be disabled While this feature can help maintain audio quality advanced users might need to dis able it This would allow full control over the Model 46 s four hybrid circuits en abling them to be used completely inde pendently A second DIP switch changes the way in which the front panel auto null push button switches operate Normally pressing one of the buttons begins the process of auto nulling both channels associated with an interface The alter nate switch mode allows each auto null sequence to be activated independently One tap of the auto null button will begin the auto null process for interface one Two taps of the button will begin the auto null process for channel two For installer selected applications three opto coupled inputs allow selected Model 46 features t
46. onnected as long as the current is limited to 20 milliamperes maxi mum If necessary an external resistor can serve to limit the current For example Issue 2 September 2007 Page 13 Model 46 Interface with a 12 volt DC signal using a 560 ohm Y4 watt resistor in series with the connec tion would be appropriate With a 24 volt DC control signal a series resistor of 1 8 k 1800 ohm is recommended For correct operation a minimum current of 2 milliam peres is recommended Access to the remote control inputs is provided by means of a 10 pin male header connector which is located on the Model 46 s circuit board Refer to Figure 3 for a view of the connector s location The keyed and shrouded header follows a common industry standard specification 2 rows of five pins each with 0 1 inch between rows and pins The mating connector is intended to be an insulation displacement IDC socket connector such as the AMP 746290 1 The connector would be crimp terminated Remote Control Inputs onto a piece of 10 conductor flat ribbon cable This ribbon cable can safely exit the Model 46 by laying flat between the chassis and the cover The ribbon cable can then fan out to loose wires or better yet be terminated onto another connector such as a 9 pin D subminiature type There are several ways of preparing to connect to the remote control inputs The easiest means is to purchase an inter connec
47. ons of this user guide for details Remote Control Inputs The Model 46 allows connection of three externally provided DC signals These signals can provide remote control opera tion of three functions auto nulling for interface 1 auto nulling for interface 2 and a special mic kill function Remote con trol of the auto nulling functions provides a resource identical to that of the front panel pushbutton switches The exact manner in which the buttons and the remote control inputs operate depends on the setting of auto null button mode configuration DIP switch The mic kill function is unique only being available using the remote control input It causes a 500 millisecond burst of 24 kHz signal to be sent se quentially to both of the 2 wire partly line interface channels associated with each of the Model 46 s two interfaces To clarify a mic kill signal is sent to a total of four intercom channels whenever the func tion is activated Independent control of sending mic kill signals to interface 1 or interface 2 is not supported User intercom devices compatible with this 24 kHz mic kill signal include RTS TW series belt packs such as the BP325 The opto coupled remote control inputs are designed for direct connection with 3 3 and 5 volt DC logic signals An internal 475 ohm resistor in series with each opto coupler s photodiode acts to limit the current flow Signals of up to 32 volts DC can be safely c
48. or 30 milliseconds then a minimum no current period of 30 milliseconds followed by current flow for a minimum of 30 milli seconds The second period of current flow must come within one second of the start of the first Once the interconnect method and the source of the control signals have been selected refer to Figure 4 for connection details Ensure that the connected signals follow the specified polarity or damage to the opto coupled inputs may occur 10 Pin 9 Pin D Sub Function Header P9 Interface Cable Remote Auto Null Interface 1 7 4 Remote Auto Null Interface 1 Remote Auto Null Interface 2 Remote Auto Null Interface 1 Remote Mic Kill o joja N oO c oj o o Remote Mic Kill Figure 4 Remote control input pin out chart Model 46 User Guide Studio Technologies Inc It s important that a competent techni cian be available to perform the actual remote control input connection process As expected mating the interconnecting cable assembly with the Model 46 s 10 pin header requires removing the unit s cover As such this must be done only after confirming that all sources of mains power have been disconnected from the unit AC Mains Power The Model 46 operates directly from AC mains power of 100 to 240 V 50 60 Hz As a universal mains input device there are no switches to set or jumpers to install A 3 pin IEC 320 C14 type inlet connector on the Model 46 mates wit
49. or too high a value will reduce the signal to noise performance And as expected it may also result in audio sig nals being sent to the 2 wire circuits at too low a level Begin a review by confirm ing that the two 4 wire level DIP switches associated with each interface are set as required If the Model 46 s 4 wire nominal levels are set correctly but the meters still reflect sub optimal levels the issue may be relat ed to incorrect settings on the equipment connected to the 4 wire inputs and out puts It S possible that although a connect ed 4 wire device s nominal level matches the Model 46 s level setting its actual nominal level may be significantly differ ent With a digital matrix intercom system this problem could be due to an incorrect configuration having been made to a spe cific channel or port For example the RTS Issue 2 September 2007 Page 21 Model 46 Interface ADAM system has a published nominal level of 8 dBu but using its configuration software it s possible to set panels or ports to a level different than nominal The best solution in this case is to adjust the inter com system so that its levels comply with its own published nominal This should at least in theory lead to the best system performance including correct interfacing with the Model 46 But often it s impos sible to clean up the levels of a existing system In this case it may be necessary to revise the Model 46 s 4
50. our times per second component refresh routine will not occur Goodbye click but hello to the possibility that an Issue 2 September 2007 Page 20 ESD induced audio path problem could occur A good rule of thumb is that if a Model 46 is mounted in an equipment rack with a known good ground connection disabling refresh shouldn t pose any risk to reliable operation But if a unit is mount ed in a portable rack or used loose as a single device refresh should always remain enabled The reasoning is quite simple the latter condition is much more likely to allow an ESD hit to dissipate into the Model 46 s enclosure while a substantial rack enclosure will offer a low impedance path for ESD energy to dissipate into Factory Test Back panel DIP switch 4 is used to select between normal mode and factory test mode When switch 4 is in its off down position the Model 46 operates in its stan dard fashion When switch 4 is in its on up position the factory test mode is selected As expected when the Model 46 is de ployed in the field switch 4 should remain in its off down position No damage to the Model 46 or connected equipment will occur when factory test mode is active Operation Technician intervention is typically not required during normal Model 46 operation The unit is designed for continuous opera tion with no routine maintenance necessary Activating the auto null functions may be warranted should co
51. s have a DC voltage pres ent typically provided by power supplies such as the RTS PS31 or Clear Com PS 232 This DC power normally 30 32 volts provides energy for connected devices such as user stations or belt packs In this type of application the Model 46 is configured to operate in its external 2 wire power source mode In this mode the Model 46 s circuitry maintains the required high impedance load and as in all cases draws no power from the party line circuit An auto terminate func tion ensures that should a wet circuit not be connected the Model 46 s interface Circuitry will remain stable This unique feature makes certain that objectionable audio signals including oscillations and squeals will infrequently be sent to the connected 4 wire device A significant capability of the Model 46 s 2 wire interfaces is their ability to supply DC power and 200 ohm AC termination to the connected intercom circuits Re ferred to as the Model 46 s internal 2 wire power source mode the 30 volt output can power devices such as user stations and belt packs In many applications this will eliminate the need for external inter com power supplies Besides reducing total system cost this feature can also lower system weight reduce required mounting space and decrease the mains energy requirement With each 2 wire interface s ability to sup ply up to 300 milliamperes of current a typical broadcast application t
52. signal from the receive signal in the 2 wire to 4 wire interface is critical The quality of this isolation technically known as return loss or trans hybrid loss is mea sured in dB A high value is important especially in applications where multiple 2 wire to 4 wire interfaces are used togeth er Remote sports broadcast applications Model 46 User Guide Studio Technologies Inc Model 46 Interface are especially sensitive to this requirement The Model 46 s sophisticated auto nulling function uses analog circuitry under mi croprocessor control to achieve significant trans hybrid loss This return loss null is achieved by making a series of adjustments to account for the resistive inductive and Capacitive conditions that are present on the connected 2 wire party line circuit The party line s conditions are the sum of the impact made by the type and quantity of cable the connected user devices and the intercom power source Whenever a user presses one of the Model 46 s auto null buttons digital circuitry ad justs the analog hybrids to rapidly achieve their maximum return loss The nulling pro cess takes less than 10 seconds for each channel of an interface However it s impor tant to note that while the nulling process is automatic it only takes place upon user request This can lead to more stable and consistent audio performance when a hy brid is exposed to the varying 2 wire condi tions o
53. significant So that the Model 46 s 2 wire to 4 wire interface circuits remain stable and don t generate audio artifacts an auto terminate feature is implemented This maintains a 200 ohm termination on both pins 2 and 3 so long as neither of the 2 wire power sta tus LEDs is lit To clarify if either or both the LEDs are lit then both terminations are removed It was felt that this method would provide a fairly accurate indication that an active intercom circuit is connect ed In this case the 200 ohm termination is expected to be provided elsewhere typi cally as part of the external power supply and the Model 46 s termination is lifted Internal Power Source When an interface s front panel DIP switch is set for internal 2 wire power the Model 46 s 2 wire party line interface supplies 30 volt DC on pin 2 of the output con nector A maximum current draw of 300 milliamperes is available This current is sufficient to power various intercom user devices such as small user stations and belt packs A common broadcast appli cation would be to use RTS BP325 belt packs Select the connected devices so that their total current doesn t exceed 300 milliamperes That s not always the easiest figure to calculate but a web search will generally find specifications for all com monly used devices For example a search finds that the original version of the BP325 consumes a maximum of 85 milliamperes of current According to this f
54. ting cable assembly from Studio Technologies Inc The cable assembly consists of a length of ribbon cable with a 10 pin socket on one end and a 9 pin D sub female on the other Contact the factory or check the website for details Alternately a competent technician can easy fabricate an appropriate remote con trol input interconnect wiring assembly An example of a partially pre made assembly Front of Model 46 Interface Figure 3 Location of 10 Pin male header connector on the Model 46 printed circuit board Issue 2 September 2007 Page 14 Model 46 User Guide Studio Technologies Inc Model 46 Interface is part number A1AXH 1036G ND which is available from Digi Key www digikey com It s important to ensure that the source of the remote control signals can meet the Model 46 s logic state and timing re quirements The Model 46 recognizes an idle remote control input as one that has no current flowing through it An active remote control input is one that has current flowing through it for a minimum of 30 milliseconds A special case arises when the auto null button operating mode has been set to independent This requires one front panel button tap to auto null channel 1 and two button taps to auto null channel 2 The remote control equiva lent for one tap is current flowing for a minimum of 30 milliseconds The equiva lent for two taps is current that flows f
55. tion of the status and level meter LEDs Mounting the Model 46 Once a mounting location has been se lected installation can begin The Model 46 requires one space 1 75 vertical inches in a standard 19 inch 48 3 cm equipment rack Secure the unit into the equipment rack using two mounting screws per side 4 Wire Audio Inputs and Outputs Two audio line input and two audio line output signals are associated with the 4 wire section of each of the Model 46 s two interface circuits Connections are made using standard 3 pin male and female XLR connectors Refer to Ap pendices A B and C for details on inter connecting with Telex RTS Riedel and Clear Com matrix intercom systems 4 Wire Line Inputs As previously mentioned each of the Model 46 s two interfaces allows two analog line level audio sources to be Model 46 User Guide Studio Technologies Inc Model 46 Interface connected The source for these signals will typically be ports on a matrix intercom system It s also possible that the signals will come from other devices such as a fiber optic or copper based audio trans mission system The 4 wire input circuitry is balanced capacitor coupled transform er isolated and has an impedance of 13 k ohms The line inputs are compatible with signals that have a nominal level of 0 4 6 or 8 dBu Configuration switches located on the Model 46 s front panel al low the circuitry to be adjusted to matc
56. wer sup plies help to ensure cool reliable opera tion in a variety of settings Design Philosophy While the bits and pieces that make up the Model 46 have been described in conventional terms the real strength of the unit rests in how it integrates and per forms in the real world Before beginning the Model 46 s design process conversa tions with industry experts quickly made it Model 46 User Guide Studio Technologies Inc apparent that installing and configuring existing 2 wire to 4 wire interface units was invariably a time consuming aggravat ing process that required the talent of an expert to achieve reasonable results And even under those constraints the resulting audio performance was often mediocre Any new design had to look at the applica tion in a different way This led to the over riding Model 46 design goal create a new breed of cat fundamentally changing how broadcast 2 wire to 4 wire interface equip ment fit into actual applications An important first step was to eliminate the requirement that a senior technician along with a screwdriver be present dur ing every installation It was universally acknowledged that their time can be better spent elsewhere The need to adjust trim potentiometers fabricate special cabling and connector straps use nulling earpiec es etc had to be eliminated For example in virtually all instances input and output levels fall within just a
57. wire nominal level settings to match the reality of the connected signals The to 4 wire meters display the level of signals that come from the 2 wire party line circuits and go out the 4 wire inter faces An issue may arise if the signals coming from the connected party line user devices aren t at a sufficient level so that a normal meter display can be reached This could be the result of an incorrectly configured 2 wire nominal audio level Confirm that the DIP switch associated with each interface is set to match the nominal level of the connected devices RTS user devices have a nominal level of 10 Clear Com devices typi cally have a 14 dBu nominal level It s also possible that an error is pres ent on the 2 wire party line circuit Signal levels associated with 2 wire party line circuits depend on a single termination being present This termination typically 200 ohms is almost always made at the power supply source But it s possible that another device such as a second active power supply on the same circuit will cause a double termination condi tion This leads to a nominal 100 ohm line impedance which will result in a level drop Issue 2 September 2007 Page 22 of at least 6 dB Removing the unwanted termination is really the only valid means of correcting the problem Connecting Party Line Devices The Model 46 s two dual channel interface circuits allow two sets of user devices t
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