Intertoll Trunk Net Loss Maintenance 



under Operator Distance and Direct 



Distance Dialing 



By H. H. FEEDER and E. N. LITTLE 



(Manuscript received March 15, 1956) 



Nearly all of the components of an intertoll trunk contribute in some degree 

 to its variations in transmission loss. Automatic transmission regulating de- 

 vices in carrier systems and in many voice-frequency systems control in- 

 herent variations in the intertoll trunk plant. These variations in transmis- 

 sion come mainly from unavoidable causes such as temperature changes. The 

 success of these devices depends on how precisely the trunk is lined up and 

 the manner in which the maintenance adjustments are made. When the na- 

 tionwide dialing plan with automatic alternate routing is in full swing, main- 

 tenance requirements will be more severe because of the material increase in 

 switched business and the number of possible links in tandem, and because 

 operator checks will not be obtained on most calls. Therefore, the maintenance 

 forces will have to keep closer watch on intertoll trunk transmission perform- 

 ance and insure that the necessary adjustments are made in the right places. 

 This article discusses some of the maintenance techniques now used and sug- 

 gests fields for further study. 



TABLE OF CONTENTS 



Page 



Introduction 956 



The Prolilem of Net Loss Maintenance 956 



Effect of Switching Plans 957 



Manual Operation 957 



Dial Operation 958 



Effect of Carrier Operation 960 



Table 1 960 



Quantitative Aspects of the Problem 962 



Table II 963 



Use of Transmission Loss Data 964 



Procedure for Analyzing Measurements 965 



Effectiveness of Over-all Trunk Test and Analysis 969 



Simple Layouts 969 



Complex Lajouts 970 



Need for Education 971 



Summary and Conclusions 972 



955 



