SWITCHING PLAN FOR TELEPHONE TOLL SERVICE 



437 



switches at Ottawa, Toronto, Chicago, Denver, Salt Lake City, 

 Pocatello and Idaho Falls, a total of seven. The chance of establishing 

 such a connection within satisfactory limits of time was, of course, 

 relatively small and the resulting circuit, when established, did not 

 permit the conversation to be held. Under the general toll switching 

 plan, this call will be routed with switches at Ottawa, New York, 

 Denver and Pocatello, a reduction of three switches. Furthermore, 

 the circuits involved in this connection will be designed with such 

 transmission standards as to give satisfactory conversation. 



Fig. 8 — Maximum number of switches under general toll switching plan. 



The routes provided by the plan for countrywide service are also 

 supplemented by more direct routes of equivalent or better service 

 characteristics in cases where the amount of business is sufficient to 

 make this economical. Furthermore, the routes to regional centers 

 are, in some cases, supplemented by alternate routes through what 

 are called "secondary outlets." These are distinguished from the 

 primary outlets in that they do not necessarily have direct circuit 

 connections to all toll centers in their areas but serve a useful purpose 

 as an alternate route for the toll centers connected to them. 



The essential features of the general toll switching plan from the 

 standpoint of the interconnection of the switching offices may be 

 summarized as follows: 



Regional Centers 



Regional centers are switching offices strategically located to cover 

 the various parts of the country and completely interconnected 

 with direct circuits, thus forming the basis of a countrywide 

 toll network. 



