972 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1956 



elude over-all objectives, inherent capabilities and limitations, and the 

 interrelation of functions of the many basic blocks comprising carrier 

 systems. Personnel so educated can approach the problems of transmis- 

 sion maintenance with understanding and avoid the maladjiistments 

 and troubles due to "man-failure" which are potential hazards in any 

 complex systems. 



SUMMARY AND CONCLUSIONS 



In summary, the problem of maintaining satisfactory transmission 

 over trunks under distance dialing involves, primarily : 



1 . Impro\dng the over-all trunk net loss stability so that the distribu- 

 tion grade does not exceed 1 db, as an initial objective. 



2. Reducing trunk loss bias for individual offices to less than ±0.25 db. 



3. Removing from operation those trunks having excessive loss devia- 

 tions before unfavorable service reactions occur. 



To do these things in the face of the increasing complexity of our plant 

 and the absence of operator surveillance will require that: 



1 . Individual systems have adequate short term stability to keep day- 

 to-day variations small. 



2. Routine tests and adjustments be made on individual systems and 

 components to correct for long-term deterioration. 



3. Frequent over-all trunk tests be made to locate trunks whose per- 

 formance is beyond acceptable limits and, as a quality control measure, 

 to monitor the performance of the trunk plant. 



4. Trunk trouble-shooting be performed on a well coordinated basis 

 to locate and correct the source of trouble. (Compensating maladjust- 

 ments must be avoided.) 



Although facilities are available and methods are known for doing 

 some of these things, considerable effort is required as follows: 



1. Study of performance of individual systems to determine capabili- 

 ties of present design and major sources contributing to over-all trunk 

 instability. 



2. Study of transmission maintenance procedures, both routine and 

 trouble-shooting, to determine the proper test intervals and how best 

 the procedures can be carried out on a coordinated basis. 



3. Development of improvements in systems and test facilities as 

 indicated by the above studies. Convenience is an important factor in 

 test arrangements. 



4. Thorough education of personnel in the over-all make-up, function 

 and interrelation of systems within the trunk plant, and in the significance 

 of transmission maintenance in pro\'iding uniformly good and depend- 

 able transmission. 



