950 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 195G 



for other purposes in the telephone plant, for example, in the computer 

 of the automatic message accounting system. It obtains the specified net 

 loss of the trunk being tested from the class relay which remains operated 

 throughout the test. When a computation is to be made of the deviation 

 in the far-to-near direction, for example, the control circuit extends to 

 the adder a number of leads from the contacts of the far-near pad control 

 relays. Some combination of the 9 far-near pad control relays remains 

 operated after the far-near pad adjustment is finished and therefore some 

 combination of the leads extended to the adder will be closed. These 

 leads furnish to the adder the measured loss of the intertoll trunk in the 

 far-to-near direction. The adder then subtracts the specified loss from 

 the measured loss and presents the answer together with the proper 

 sign, -|- or — , to the teletypewriter for a printed record. The deviation 

 in the near-to-far direction is computed in the same manner by extending 

 corresponding leads from the near-far pad control relays to the adder 

 at the proper time. 



Deviation Registers 



In determining bias and distribution grade by the method discussed 

 in the companion article,* the deviations from specified net loss are cal- 

 culated for each measurement. These deviations are grouped together in 

 0.5 db increments from +8 db to —8 db, all deviations exceeding +7.8 

 db or —7.8 db being considered as -(-8.0 db and —8.0 db respectively. 

 For example, all deviations of -|-0.3 db to -f-0.7 db, inclusive are con- 

 sidered to be -f 0.5 db and are so tallied on the data, or stroke, sheet. 



To assist in this work the automatic test equipment includes thirty- 

 three manually resettable counters corresponding to the 0.5 db incre- 

 ments from -f-8.0 db to —8.0 db inclusive. Just prior to a transmission 

 test cycle all these counters are reset to zero. At the time a deviation 

 computation is made, the computer also causes the proper counter to 

 register one count. After the test run on a group of trunks, the counter 

 readings can be transcribed directly as the final tally on the stroke sheet 

 and may be used to determine the bias and distribution grade. A "total 

 tests" coimter keeps a tally of all the computations. At the end of the 

 test run the total count serves as a check of the total count of the other 

 33 counters. 



Check for Excessive Deviations 



In addition to obtaining data for the calculation of bias and distribu- 

 tion grade, the maintenance forces would also like to know promptly 



* H. H. Felder and E. N. Little, Intertoll Net Loss Maintenance Under Opera- 

 tor Distance and Direct Distance Dialing, page 955 of this issue. 



