INTERTOLL TRUNK NET LOSS MAINTENANCE 



957 



it is the best solution to the transmission and economic problems. How- 

 ('\er, carrier involves many more variable elements and requires higher 

 precision of adjustment than voice-frequency systems need. These in- 

 crease the difficulty of maintaining trunk losses close to design values on 

 a day-by-day basis. 



Third, as operator distance and direct distance dialing grow, there is 

 constantly diminishing opportunity for operators to detect and change 

 unsatisfactory connections or to report unsatisfactory transmission con- 

 ditions to the appropriate testboards for action. 



Thus the maintenance problem is in two parts: 



1. How can we reduce departures from design standards even in the 

 [face of increasing complexity of plant? 



2. What substitute can we find for operator detection of troubles, and 

 can we find even better means of detection? 



The ways in which switching plans and the use of carrier reflect upon 

 Ithe problem of trunk net loss maintenance is discussed in more detail in 

 the follo\\dng sections. 



EFFECT OF SWITCHING PLANS 



Manual Operation 



For many years long distance traffic has been handled on a manual ba- 

 sis under the "general toll switching plan" illustrated in Fig. 1. Between 

 two points indicated by toll centers, TC and TC", it was theoretically 

 possible to get as many as five trunks in tandem. This rarely occurred be- 



RC' 







Po'(>: 



I"- 



TC 



■& 



.'I 



.1. 



I 



! / 





^^. 



RC" 



"O PO" 



\ 

 "-A 



■B TC" 



TC = Toll Center PO = Primary Outlet RC = Regional Center 

 Fig. 1 — General toll switching plan — manual operation. 



