INTERTOLL TRUNK NET LOSS MAINTENANCE 



961 



ALPHA 



BETA 



GAMMA 



* TO THIS OR OTHER DESTINATIONS 



Fig. 3 — Typical carrier channel assignments. 



points even though circuit requirements to a given point are sufficient to 

 utilize 12 or more channels. This is done to minimize the chances that all 

 of the trunks between two points will be interrupted by a system failure. 

 A simple case is illustrated by Fig. 3 which shows trunks between Alpha 

 and Gamma connected at an intermediate point, Beta, in such a manner 

 that a failure in any one of the systems A, B, C, or D will affect only 

 half the trunks. 



This routing problem, however, complicates the maintenance problem. 

 For example, if trunk Tl were found to have excess loss in the Alpha- 

 Gamma direction it could be corrected by raising the channel gain at 

 Gamma. On the other hand, a correct diagnosis might have disclosed that 

 the trouble was due to a repeater in system A. If this were the case, 

 merely compensating for the excess loss in Tl by changing the channel 

 gain would still leave all other trunks associated with system A in 

 trouble. Later on, if the repeater difficulty were corrected, and no further 

 action were taken, the net loss of Tl would then be too low. 



Thus, the flexibility which is so desirable to minimize interruptions of 

 whole circuit groups leads to a difficult problem in the administration of 

 trunk loss adjustment and maintenance. Furthermore, because of the 

 larger numbers and greater dispersion of trunks and terminal points, the 

 situation in the actual telephone plant is much more complex than in the 

 above example. Also, the diagnosis of trouble conditions is made more 

 difficult by the normal variations of channel losses in the carrier systems 

 and consequently of the trunk losses about their design values. This can 



