BEI.I. SYSTEM Tl-CIIMC.-IL JOLR.X.-iL 



fliniin.iud l>\- tlio ri-niil.ir m.iiiiUiiaruc work. Missini; iqiiipniciU 

 will in (-iTt.iiii rases causi' a yaiii in transmission Imi aftccls (Ik- circuits 

 advcrst'U- in other wa\s. 



Typical examples of connnon irouliles. willi the excess losses wiiicli 

 they cause, are given in the following table: 



Type of Circuit 

 and Equipment 



Repeating coils in 

 cords, incoming 

 trunk circuits, select- 

 ors, toll connectors 



Su|>ervi>>or>' relays in 

 "A" corii circuits 



Bridged retardation 

 coils or relays in toll 

 cord circuits, coni- 

 (losite sets, connect- 

 ors ami slep-by-stcp 

 repeaters 



l< e () e a t i n g coils on 

 loatknl toll switching 

 trunks 



Iniluction coils in op- 

 erators' telephone sets 



Cause of 

 Trouble 



KIc-clrical defects 



(dcnerally short cir- 

 cuited turns) 



Incorrect wiring (Gen- 

 erally reversed wiml- 

 ings) 



KIcctrical defects 



(f) p c n non-inductive 

 winding) 



Klc-ctrical clefc-cts (Gen- 

 i-rally short circuited 

 turns) 



Wrong ty|)C of cfjuip- 

 ni cut, incorrect wir- 

 ing 



Klectrical defects. In- 

 corri-ct wiring 



Approximate Excess 

 Transmission Loss' 



1.5 to 5.0 TU 



2.0 to l.S.O TU 

 .\l)out 2.5 TU 

 1.0 to 5.0 TU 



1.(1 to 4.0 TU 

 1.0 to 1,?,0TU 



There are, of course, many other specific types of troubles delected 

 by transmission tests which give definite quantitative losses but the 

 al)ove will serve to illustrate the value of this testing work in eliminat- 

 ing excess losses in a telephone plant. 



Muintename Features Peculiar to Telephone Repeaters and Carrier 

 Systems. The siime classification of troubles discussed above applies 

 to repeaters and carrier systems. Amplifier equipment, however, 

 employs certain feattires which are not common to the more simple 

 telephone circuits and stjme of the troubles which may occur if the 

 pro[KT maintenance procedures are not followed will seriously affect 

 servite. It is for this reason that repeater and carrier installations are 

 pr<j\i<led with s|K'cial testing e(|uipment which is always available 

 for use either in routine maintenance or in locating and clearing 

 any trtmbles which may occur in service. Automatic regulating 

 devices arc also provided where\er this is practicable in order to 

 reduce to a minimum the amoimt of manual rcgulailDii and 

 maintenance. 



' \V. M. Martin, " I'lu- TransniiMion Unit," Jnunml oj the A. I. E. E., June 1924- 

 H. S. r. J., \\,\. 111. p. 400. 1924; C. \V. Smith, "Practical Application of Trans- 

 niimion Unii, ' W. .V. /. J.. Vol. Ill, ji, 4<W, l')24. 



