1166 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



4. Provision for stopping the test cycle to enable the tester to per- 

 form manual operations such as inserting a test plug in a jack on the 

 unit or insulating relay contacts in order to isolate portions of the cir- 

 cuit for test simplification and to obtain a more detailed test. 



5. Provision of improved lamp indications to aid the tester in clearing 

 wiring faults or in locating defective apparatus. These would include 

 the necessary information as to which test set circuits are connected 

 to which unit terminals as well as which relays of the wired unit should 

 be operated at that stage of the test cycle. 



6. Provision for connecting several terminals of the unit under test 

 together as a means of providing circuit continuity where required. 



7. Provision for measuring resistance values of circuit components. 



8. Provision for insertion of various resistors in battery or ground 

 leads to control currents to desired values. 



9. Provision for checking voice transmission paths through non- 

 metallic circuits such as transformers or capacitors. 



10. Provision for measuring circuit operating times in steps of ap- 

 proximately 100 milliseconds. 



11. Provision for sending and receiving dial pulses. 



12. Provision for a single code for releasing all test connections and 

 conditions previously established by the coded tape as a means of quick 

 disconnect. This is in addition to the release of individual connections 

 mentioned in (1) above. 



13. Provision for audible and visual indications of completion of a 

 successful test cycle. 



Through the use of two letters (each of which has its own combination 

 of the five holes) for each signal it was possible to obtain the over 500 

 codes required to control all test and switching functions even though 

 the teletype keyboard has only 32 keys. The only Teletype transmitter 

 (tape reader) available when the test set was first designed operated 

 at a speed of 368 operations per minute and was arranged for sequential 

 read out on two wires by means of a commutator. Conversion to five 

 wire operation and removing the commutator permitted reading each 

 row of holes simultaneously. The gearing was also changed to permit 600 

 operations per minute but even so the hole reading contact dwell time 

 was increased from approximately 20 milliseconds to 70 milliseconds for 

 more reliable operation with ordinary telephone relays. 



The machine which was designated as the Tape-0-Matic* test set, is 

 shown in Fig. 8 in operation on a typical wired relay unit mounted in 

 its shipping frame. The contact fixture is attached to the unit terminal 



* Patent No. 2,328,750. 



