AUTOMATIC TESTING OF INTERTOLL TRUNKS 949 



loss of the trunk plus the loss of the transmitting pad at the far end. 

 Since the transmitting pad loss equals the trunk loss in the near-to-far 

 direction, the difference between the measurements in Step 3 and Step 2 

 is the trunk loss in the near-to-far direction. After about 10 seconds the 

 far end removes the test power and starts the noise check in the same 

 way as if this were a full automatic test. 



When the far end removes the test power after Step 3, the attendant 

 leaves the connection intact until the cord supervisory lamp lights to 

 indicate completion of the noise check at the far end. A flashing lamp 

 indicates that the noise at the far end exceeds the prescribed limit and a 

 steadily lighted lamp indicates the noise at the far end is below this 

 value. A noise test at the near end may be made by the attendant if he 

 judges, after a listening test, that a noise test is desirable. For this test 

 he uses the standard noise measuring equipment. 



PRESENTATION OF TEST RESULTS 



When making operational tests and a Teletypewriter is not being used, 

 troubles are registered by means of an audible alarm and accompanying 

 display lamps. When making transmission loss measurements, however, 

 a complete record of the measurements on all trunks tested, both good 

 and bad is frequently needed. A Teletypewriter then becomes a practical 

 necessity; otherwise the attendant would be required to supervise the 

 automatic equipment continuously and to record, from a lamp display 

 or similar indication, the results of each measurement as it was made. 

 Having provided the Teletypewriter for transmission testing, its ability 

 to print letters to represent trouble indications is utilized to avoid halt- 

 ing the progress of the tests when operational troubles are experienced, 

 except when completely inoperative conditions are encountered. 



Computer Circuit 



As mentioned earlier intertoll trunk transmission performance is 

 rated in terms of bias and distribution grade which are calculated from 

 the deviations of the measured losses of the intertoll trunks from their 

 specified values. For such calculations the maintenance forces are, there- 

 fore, more interested in the deviations than they are in actual measured 

 losses. Accordingly, the automatic transmission test and control circuit 

 at the near-end has a computer built into it which will compute the 

 deviation for each measurement so that the deviation can be recorded 

 by the Teletypewriter. 



The computer is a bi-quinary relay type adder similar to those used 



