INTERTOLL TRUNK NET LOSS MAINTENANCE 971 



The scope of the trial was then limited to a smaller group of intertoll 

 trunks which could be given close attention. The 42 trunk group between 

 Washington, D.C., and Atlanta, Ga., was selected and these trunks were 

 put through rigorous circuit order tests and adjustments approaching 

 the completeness of initial line-up tests. A test cycle composed of trans- 

 mission loss measurements made on the 42 trunks in both directions 

 was performed four times daily for a period of about five months. During 

 the period covered by this phase of the trial, adjustments were made 

 only as indicated by carrier pilot ^'ariations, by deviations from specified 

 net loss large enough to operate the limit feature of the automatic trans- 

 mission test and control circuit, or with other trouble clearance. 



The tests for each day were analyzed as a group. On the first day the 

 distribution grade of the deviations from specified net loss for the group 

 was 0.8 db and the bias was +0.5 db. On the last day the distribution 

 grade was 1.2 db and the bias was —0.25 db. For the entire group of 

 measurements (584 test cycles), the distribution grade of the deviations 

 was 1.26 db and the bias was —0.08 db. This represented a substantial 

 improvement over the results obtained in the first phase of the trial. It 

 showed that a great deal can be accomplished by improving the circuit 

 order procedures and increasing the thoroughness with which they are 

 carried out. 



It was found that combination carrier trunks composed of perma- 

 nently connected links, thus not having the benefit of control by ter- 

 minal-to-terminal pilots, have more variability than individual trunks 

 having over-all pilots. Adjustment of such combination trunks requires 

 coordinated action at the various pilot terminals through which the 

 trunk passes, in order that readjustment of the over-all trunk loss can 

 be made at the point in the system responsible for the deviation. In the 

 case of many route junctions, the complexity of the layout makes it 

 difficult to coordinate the necessary measurements at several points so 

 that the proper point for adjustment can be determined. 



NEED FOR EDUCATION 



The complexity of carrier system layout as indicated above, has im- 

 posed a difficult task on the plant transmission maintenance forces. Al- 

 though our present transmission maintenance practices seem to be ade- 

 cjuate for systems in simple layouts, some expansion appears needed for 

 the more complex layouts. This will recjuire further study. 



It is important to keep in mind, however, that the pro\'ision of good 

 practices and training of personnel in following the detailed steps therein 

 are not in themselves sufficient to assure good transmission maintenance. 

 There is an additional need for education of plant personnel in fundamen- 

 tal considerations affecting operation of carrier systems. This must in- 



