AUTOMATIC TESTING OF RELAY SWITCHING CIRCUITS 



1175 



reuse. A final code SC must be put in every tape to operate the OK 

 lamp and gong if a successful test cycle has been performed or conversely 

 to indicate that the tape should be re-run if trouble has been found 

 and cleared during the test cycle to be certain that no new faults have 

 been introduced. 



Preparation for testing a particular wired relay unit requires only the 

 selection of a test cable one end of which is equipped with a suitable 

 contact fixture for attachment to the unit terminal strip and the other 

 with a gang plug for connection to the set. The proper tape is selected 

 from a nearby file cabinet and inserted in the gate of the tape reader 

 as shown in Fig. 15. The tape is stored in a cardboard carton 3^^ X 4 



Table I 



Feature Numbers 



1 and 2 



3 and 4 



5 through 19 

 20 



21 and 22 



23 and 24 



25 through 34 

 35 



36 and 37 

 38 and 39 



Description of Functions 



High sensitivity relay circuit. Simulates 1,800-ohm sleeve 

 circuit for busy test and general continuity through high 

 resistance ciruits. 



Simulates the distant tip and ring terminations of a subscriber 

 or exchange trunk. Provides for ringing, tone receival, dial 

 pulse sending, line resistance, high-low or reverse battery su- 

 pervision, pad control, continuity, and resistance verifica- 

 tion. 



Auxiliary tip and ring circuit for holding, checking continu- 

 ity, receival of tone on four wire or hybrid coil circuits. 

 Loss range of less than 0.5 db, 0.5 to 1.5 db, 1.5 to 6 db and 6 

 to 15 db can be checked. 



Direct connections for supplying any of the ten terminating 

 conditions. 



Simulates low or medium resistance sleeve circuits for margi- 

 nal tests. 



Simulates the local tip and ring terminations of a switch- 

 board or trunk circuit. Provides for ringing and dialing re- 

 ceival, high-low reverse battery supervision, transmission 

 pad control, tone transmission, continuity and resistance 

 check by balance. 



An auxiliary tip and ring circuit for holding, checking con- 

 tinuity, tone transmission on four-wire hybrid coil circuits. 



Low sensitivity relay circuits for general continuity checking. 



A circuit for checking balance on the (M) lead of composite or 

 simplex signalling circuits and for checking receival of none, 

 one or two pulses. 



Medium sensitivity relay circuits for continuity checking. 



Direct connections for supplying any of the ten terminations. 



