ni.i.i. srsTi-.M inciiMc.iL jovrnal 



the telephone repeaters out of one circuit or having available a non- 

 repoatcre<i or non-carrier circuit, since the gains of the repeaters in 

 the two directions intrtxiuce variable factors in the overall equivalents 

 which do not permit triangulation computations to be made. The 

 overall tests on the carrier circuits do not differ in any way from 

 the tests on repcateretl or non-rei)eatereti circuits, each carrier channel 

 iK'inn testeil as a separate circuit through the switchboards. The 



.e 



Vi 



l-.K. .i .\l..pMn 



HIS In Hull .Sysuri 

 Measuring .Sets 



>l I'riiiMiient Transmission 



me;isuring current is modulad-d and demodulated in the s;ime manner 

 as voice currents under regular operating conditions and the measured 

 if|uivalent, therefore, indicates the overall transmission efficiency. 



The map of I-'ig. 3 shows the locations in the Bell System of trans- 

 mission measuring sets of the general type described above. At a 

 number of the larger toll centers, such as New York and Chicago, 

 where the number of toll circuits to be tested require it, several trans- 

 mission measuring sets are installed. There arc now in operation 

 ln'twii-n -10 anfl .">() of these sets, making it possible to test all of the 

 longer and more important toll routes in the system. The shorter 

 toll circuits radiating out from the large toll centers are also tested 

 with tlies<' s;mie sets. At the smaller clTiccs where fixed transmission 

 measuring sets are not warranted, the toll circuits which cannot be 

 I)icke<i up liy the larger oftices arc tested by portable transmission 



