838 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1952 



to as intertoll trunks or lines but are classed as toll connecting trunks. 



Where the volume of traffic warrants, direct circuits may be pro\'ided 

 to by-pass the intermediate switching points included in the preceding 

 example. Once such direct circuit groups have been established, it is 

 economical and advantageous from a switching standpoint to take 

 advantage of their existence, using routes that involve a minimum num- 

 ber of switches. The basic routing plan is used when the more direct 

 circuit combinations are busy. 



These routing arrangements contemplate the application of "high 

 usage" and "final" trunk groups as an integral part of the plan. The 

 "high usage" groups are direct groups which by-pass the higher order 

 switching points wherever the routing of the call permits. These "high 

 usage" groups can be engineered to cany high loads per circuit, with an 

 adequate number of circuits in the "final" groups to take care of prac- 



REGION 2 



KEY 



A 

 O 



Fig. 6- 



O TC- ORDINARY TOLL CENTER 



FINAL GROUP 



POSSIBLE HIGH USAGE GROUP 



SC- SECTIONAL CENTER 

 PO- PRIMARY OUTLET 



-Illustration of intertoll routing pattern between two regions. 



''|'^'|1!£- >ROUTING SEQUENCES 



