lEU-.rnosi-. ih!.i\sMissi(>\ m.iim i.x.im i. a.\ 



mon- rii;i(l Incal m.iiiiti-ii.mcf r<iiiliiio> |),i\ini; |).irlinil.ir .iiiciilinii to 

 thf ly(H' of ririuits in wliirli llic iroulik-s .irt- Inc.iii'd. I'lu- |)<-i- 

 ifiitano of Class B troiil)U's is not as a ruU- as liinh as tlu- ("lass A 

 troul)lt's aiul I'xixTiencf lias shown lliat wlu-n ("lass H trouMis an- 

 oiH'v clinun.ttt.'(l by transmission tcslinn ini'iluxls only itifrr(|iu'nt 

 siibsi'cim-nt tvsts are rr(|uirf(l to take care of an\- additional troubles 

 of this class which may get into the plant. 



In determining what constitutes an excess loss, the value of tiie 

 transmission as well as the practical design and manufacturing con- 

 sitierations to meet o|x'rating limits are taken account of. An excess 

 gain is also considered as a trouble on circuits etjuippeil with ampli- 

 fiers, since this may produce poor (juality of transmission which is 

 likely to be more detrimental to service than an excess loss. The 

 value of transmission based on economical design considerations 

 varies, depending on the first cost and annual charge of the particular 

 types of circuits involved. A gain of one TU in the toll plant is 

 generally worth more, for example, than one in the local plant, since 

 it ccsts more to provide. In transmission maintenance work the 

 cost of making transmission tests and clearing trouble is i)alanced 

 against the \alue of the transmission gained for the [>urposc of est.ib- 

 lishing economical transmission limits to work to. 



Speiijic Examples of Common Troubles Found and Their Effect on 

 Transmission. Certain kinds of troubles which are detected by 

 transmission measuring sets do not cause excess losses which can be 

 quantitatively measured. Such troubles are, however, readily de- 

 tected by "ear balance" transmission measuring sets in that the\' 

 cause noise or scratches and by the "meter balance" sets from fluctu- 

 ations cf the needle of the indicating meter. The most common 

 trouble of this kind is due to cutouts or opens which may be caused 

 by dirty connections, loose connections, improper key and relay 

 adjustments, etc. While not causing a quantitative value of excess 

 loss, this class of trouble is very detrimental to transmission and 

 more serious in many instances than fixed excess losses. Indeter- 

 minate troubles of this nature are gi\en an arbitrary excess loss \aluc 

 based on experience. 



Considering troubles which gi\e definite losses, the most common 

 kinds are caused by electrical defects in equipment, incorrect wiring 

 of equipment in circuits and wrong types of equipment. The other 

 classes of troubles, such as crosses, high resistances, and low insula- 

 tion, also generally give measurable excess losses but these are not 

 as common in the plant, since troubles of this nature are more likely 

 to affect the signaling and operation of the cirrin'ts and are, therefore. 



