32 HF.u. sysrr.M jhcusical jovrsal 



ill the circuits wliicli h.ixc to be given particular local attention in 

 maintaining the overall transmission efficiency. Since both tele- 

 phone repeaters and carrier employ the s;ime tyjies of vacuum tubes 

 with very similar arrangements for power supply, the maintenance 

 requirements for the two are nnich the s;ime. The chief items to 

 be observed in both carrier and reiK-atcr maintenance are that the 

 gains specified to give a desired oxerall transmission equivalent be 



I rlHi^i—^ ^ ' * — ' 



Pot.enlt»i"«t«r 



n«i« Cwrfwtt and Ml«f« S31Cir^««l B«1ar«« Tnt* 



hij;. 5 — Sihmiatic Diugram of a 22-Typc Telephone Re|)eatcr Showing Important 

 Local Transmission Maintenance Tests 



kept as constant as possible, that these gains remain fairly uniform 

 within the range t>f frecjuencies invoh'ed, and that conditions do not 

 exist which will ilisiurb the overall balance between the circuits 

 and networks sufficiently to cause i)o<)r quality of transmission. 



Consi<iering telephone repeater maintenance, Fig. 5 shows a sche- 

 matic diagram of a 22 type repeater antl indicates the important 

 tests which are made locally to insure that the apparatus is function- 

 ing in a s;itisfactor\ manner as a part of a toll circuit. The numbers 

 applied to the dilTerent tests listed in the figure show approximateh 

 the |)oints in the rejH'ater circuit at which the tests arc made, the 

 piir(>oses of the tests being evident from their names. 



When carrier opi-ration is applied to toll circuits, an additional 

 tr.insmission system is introduced involving the use of currents of 

 higher freriuencies than those in the voice range. From a main- 



