HP 4938A User's Manual
Contents
1. HEWLETT PACKARD NETWORK CIRCUIT ACCESS TEST SET Guide HP Part No 04938 90006 Microfiche Part No 04938 90007 PRINTED IN U S A 4938A CONTROLS RING TESTING amp AMANRE amp INDICATORS DOP SIMULATOR SX ACCESS m DALGINATE CRINGER LOADS O sm LOOP SIGNAL TE AENG TRIF LOOF SNO START LOCOT 23 22 21 2019 18 17 16 15 14 13 1 LINE switch Applies power to the instrument when in the ON position 2 RING Selects frequency of ringer voltage Up is 20 Hz and Down is 30 Hz 3 OFF HOOK Indicates that a DC loop has been closed across the TERMINATE CIRCUIT Jack and that a current of at least 17 mA typically is fiowing i 4 SIMULATE Up is 48 volt battery simulator 48 volts Tip to Ring Down is 20 or 30 Hz ring voltage superimposed on 48 volte 5 T R REV Tip Ring Reverse Up position the Tip and Ring are connected fo the TERMINATE CIRCUIT Jack in normal polarity Down position the Tip and Ring are connected to the TERMINATE CIRCUIT Jack in reverse polarity 6 OPEN Opens circuit Up position the TERMINATE CIRCUIT Jack is connected Down position the TERMINATE CIRCUIT Jack is disconnected 7 TERMINATE CIRCUIT jack Provides connection between the TERMINATE CIRCUIT functions and the circuit under test 8 Simplex Lead Patch Switch Provides an internal connection between either the TERMINATE or ORIGINATE functions and the SIMPLEX TRANSFORMER The slide switch DOSHIONS are e Up position con2. ORIGINATE CIRCUIT JACK VOLTS 330 141 5 WATT VOLTAGE MONITOR rip BINDING N Q POSTS H SOET Pen 2uf COM ah Connect the circuit under test to the Originate Circuit Jack 2 Press the REN3 push button e This wilhierminate the circuit with Ring Equivalent Number 3 load e The Voltage Monitor binding posts are also placed across the REN3 lead CAUTION The Voltage Monitor may have live Ring Voltage 3 Connect a Multimeter across the Voltage Monitor to measure Ring Voltage Testing for Ring Trip With the circuit under test terminated with REN3 and Ring Voltage present from the far end press the TRIP push button fo cause a Ring Trip closure no it Ring Trip capability of the far end generator is operational Ring Voltage monitored across the Voltage Monitor jacks should stop 4938A CONTROLS r N C ORIGINATE CIRCUIT JACK n 0 L Loop i 430 Cy 21 5 WATT R Loop Start Originate 1 Connect the circuit under test to the 4 Originate Circuit Jack 2 Press the LOOP push bution to cause a 5 loop closure on the circuit 3 The circuit May be monitored tor dialtone by connecting a Tel Set across the fine 4 Optional The loop circuit may be momentarily broken by pressing the LOOP push button The multimeter must not be connected to the Current Monitor binding posts Measuring Loop Current i Connect a Multimeter across the Loop
3. Current Monitor binding posts 2 Setihe Multimeter for DC current 100 mA range or equivalent 3 With the LOOP push button pressed as i above press the LOOP push button e The Loop Current Monitor binding Di posis will be placed in series with the circuit while the LOOP I push bulton is held down Ground Start Originate 1 Connect the circuit under test to the Originate Circuit Jack 2 Press the LOOP push button 3 Press the GND START push button 3 momentarily e A ground will be placed on the Ring 4 conduetor of the Originate Circuit Jack through the margin test resistance mm RING TESTING amp 4 WIR amp INDICATORS ppp simutatoRi SX ACE 3 my MILLTAMP METER im A LOOP CURRENT MONITOR BINDING POSTS gA LOOP SIMULATOR 0 60 amp 0 120 mA SCALE AMPS The circuit may be monitored for dial tone by connecting a Tel Set across the line If the 4938A is not connected to the AC line ground reference the unit by cor necting a wire fromthe Ground Reference Binding Post to a suitable ground point Battery Simulator 220 Q TERMINATE CIRCUIT T 48 VDC Connect circuit under test to the Terminate Circuit Jack With the SIMULATE button in the up position 48 VDC will be applied to the Terminate Circuit Jack e The OFF HOOK LED should be off until a DC loop is closed on the far end When a DC loop is closed onthe circuit and the Loop Curre
4. ONTROLS i RING TESTING amp A amp INDICATORS LOOP SIMULATOR TERMINATE CIRCUIT 220 Q A WIRE SX ACCESS Other 4 Wire Access 1 4 wire access using signaling not available in the 4938A may be accomplished by connecting the source of external signaling to the SX SXI jack 2 Be sure to move the Simplex Lead Patch Switch to the Open middie position to disconnect the Terminate or Originate functions from the Simplex Leads 4 Wire Transmission Testing 1 Connect the 4 wire circuit under test to T R and T1 R1 on the Telco side of the Simplex Transformer 2 Connect the Transmission Impairment Measuring Set to TRMT and RCV on the Test side of the Simpiex Transformer 3 Follow the procedures for 4 wire access to use signaling functions internal to the 4938A or to patch in functions from an externai source i 4 Perform the necessary Transmission Tests
5. ed in connecis 430 ohms across the loop circuit i TRIP Push push switch thai when pressed in connects 330 ohms across the loop circuit REN3 Push push switch that when pressed in applies a load to the circuit that is equivalent to the load of three ringers The voltage can be measured across the VOLTS and COM binding post Monitor Binding Posts e VOLTS Access fo monitor ring voltage ram far end generator or to monitor dial tone after affecting ioop closure e COM Common connection for voltage or current monitor AMPS Access to monitor loop current e GND Chassis ground Connection for power cord CONTROLS i RING TESTING amp 4 WIRE amp INDICATORS LOOP SIMULATOR SX ACCESS TWO WIRE CIRCUIT TESTING Sending Ring Voltage 220 NQ tem R Pe TERMINATE 20 OR 30 Hz CIRCUIT JACK 48 VDC L Connect the circuit under test to the Terminate Circuit Jack 2 Select the Ring Voltage frequency 20 or 30 Hz 3 Press the SIMULATE push button to begin ringing e Ring Voltage will be impressed on the circuit under test it that circuit is open for DC CAUTION The Terminate Circuit Jack has live Ring Voltage 4 To restart the Ring release the SIMULATE push button fo the up position Then push the button to the down position e Ringing will not restart if the DC loop is siill closed Terminating and Measuring Ring Voltage AC VOLTMETER O100V rms 2uF
6. nects the TERMINATE functions to the SIMPLEX TRANSFORMER e Middle position disconnects the SIMPLEX TRANSFORMER from both the TERMINATE and the ORIGINATE functions Down position connects the ORIGINATE function to the SIMPLEX TRANSFORMER ass BE 20 at 4938A SX SX1 Jack Simpiex lead SX is the Tip and lead 5X1 is the Ring SIMPLEX TRANSFORMER Provides 4 wire network access with Simplex leads SX SX1 The front panel graphics show the internal connections TELCO Jack Output from transformer to telephone company circuits TEST TRMT Jack input lo transformer from test equipment TEST RCV Jack Output from transformer fo test equipment TELCO Jack Input to transformer from telephone company circuits CIRCUIT FAULT LED Indicates that a circuit fault a short or a high foreign voltage exists on the circuit being tested The internal protection circuit will automatically disconnect the instrument from the faulty circuit The fault must be cleared before continuing with the testing ORIGINATE CIRCUIT Jack Provides connection between the ORIGINATE CIRCUIT unctions and the circuit under test LOOP t Momentary switch that when pressed interrupts ine Tip Ring loop closure and places the MONITOR COM and AMPS binding posts in series with the loop for measuring loop current GND START Momentary switch that when pressed grounds the ring through a load of 550 ohms LOOP Push push switch that when press
7. nt is greater than 16 mA the OFF HOOK LED will go on The Battery Simulator may be reversed uy pressing the T R REV switch The Battery Simulator may be removed from the circuit by pressing the OPEN switch MILLE AMP METER 080 amp SCALE ab eee COM CURRENT MONITOR te N C BINDING POSTS op gii AMPS GROUND START N O 9 550 Q 5 WATT oie 4 Wire Loop Start Originate 1 Move ihe Simplex Lead Paich Switch to ihe down position Connect the 4 wire circuit under test ic T R and Ti R1 on the Telco side of the Simplex Transformer Press ihe LOOP pushbutton to cause a loop closure on SX SX1 Optional The loop circuit may be momentarily broken by pressing the LOOP push button The multimeter must not be connected to the Current Monitor Binding posts Measuring Loop Current Across SX SX1 1 Move the Simplex Lead Paich Switch to the down position 2 Connect the 4 wire circuit uncer test to T R and T1 R1 on the Telco side of the Simplex Transformer 3 Connect a Multimeter across the Loop Current Monitor jacks LOOP N O _ LOOP 430 O 1 5 WATT NIRE CIRCUIT TESTING TELCO t TEST 3 1 F F T SX A i TRMT a R tas R ORIGINATE CIRCUIT JACK Tet TI Oe 0 Ti R SX 1 8 RCV cf RI io RI Set the Multimeter for DC current 100 mA range or equivaient With the LOOP push button pressed as above press the LOOP push button e The Loop C
8. urrent Monitor jacks will be placed in series with the circuit Note that if a Tei Set is used to monitor dial tone through the Voltage Monitor binding posts the dial tone will be interruptec while the LOOP switch is heid down 4 Wire Ground Start Originate 1 Move the Simplex Lead Patch Switch io the down position Connect the 4 wire circuit under test to T R and Ti Rl on the Telco side of ihe Simplex Transformer Press the LOOP push button Press the GND START push button momentarily e A ground will be placed on the Ring conductor or SX1 lead of the SX SX1 jack through the margin test resistance 48 VBC 20 OR 30 Hz ACK 86V rms Ring Simulation on 4 Wire Circuits 1 Move the Simplex Lead Patch Switch to the up position 2 Follow the procedures for Ring Simulation described for 2 wire circuits via the Terminate Circuit Jack Battery Simulation on 4 Wire Circuits Move the Simplex Lead Paich Switch to the up position ae 2 With the SIMULATE button in the up position 48 VDC will be applied to the SX SX1 jack e The OFF HOOK LED will be off until a DC loop is closed on the far end e When a DC loop is closed on the circuit and the Loop Current is greater than 16 mA ihe OFF HOOK LED will go on 3 The Battery Simulator may berreversed by pressing the T R REV switch 4 The Battery Simulator may be removed from the circuit by pressing the OPEN switch 4938A C
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