TEU-rnoM-: m.txsMissiox m.umf.n.-ixce 45 



Thf imjK)rtant elemcnls in both repeaters and carriers wliieli may 



directly affect tr.in>.ml^si(>n or iMiisf service troubles in olhcr ways 



are as follows : 



Filamiin H.iiuru^ I'litcntiomctiTs 



Plate Rattcriis l"iltirs 



("■rid Batteries Transmission Kqualizers 



\'acuuni Tubes Signaling Kquipnient 



Balancing K(|ui|>nu'iil Tatching Arrangements 



The tests oiillineil in the nuiin body of tiie paper aim lo insure 

 that tile above essential |)arts of repeater and carrier circuits are 

 functioning properly and that the equipment as a whole is giving 

 the desired results in overall transmission efJiciency. 



CoNCLfSION 



The aluive discussion of testing methods and tlio results ticcom- 

 plishcd indicate how a comprehensive and economical transmission 

 maintenance program can be applied to a telephone plant to check 

 the volume efficiency of the circuits against the established standards. 

 Consideration is continually being given to new testing methods and 

 their applications in order that further improvements in service ma>- 

 be effected and increased economies in testing taken ad\'antage of. 



AI'I'KXDIX A 



f*KiN(iPi,i:s OF Testing Methods Closely Associ.\ri;i) uiiii 

 Tr.wsmissiox Efficiency Tests 



Tests of \olume efficiency often need to be supplemented by other 

 methods of testing in transmission maintenance work. Transmission 

 efficiency both as regards volume and quality may be seriously affected 

 by noise or crosstalk, and tests for an\' conditions of this kind are 

 therefore important in maintenance work. Furthermore when 

 efficiency tests show excess losses or unsatisfactory circuit conditions 

 other testing methods prove very valuable in locating the cause. 



To illustrate this phase of transmission maintenance the principles 

 of some of the more important testing methods are briefly described 

 below. Two of the tests employ a method very similar to loop trans- 

 mission testing while others employ the well known "null" method. 

 A special method employing three winding transformers and ampli- 

 fiers widely used to determine impedance balance conditions between 

 lines and networks is also described. Several methods which involve 

 simply current and voltage measurements have lieen mentioned in 



