connection between any two points. It is the purpose of the General 

 Toll Switching Plan to provide a general design of the toll plant which 

 meets these requirements and which, therefore, when fully effective, 

 provides for satisfactory service between any two points in the conti- 

 nental United States. The Plan also covers that part of Canada 

 served by the Bell Telephone Company of Canada. For most of the 

 messages, where volume of business and other conditions justify, 

 the telephone service is of course better than the minimum contem- 

 plated by the Plan as, for example, by the provision of direct circuits. 



In addition, trends in the construction of toll circuits were such 

 that there was a growing need for an underlying plan for routing toll 

 circuits in such a way as to provide for the most economical plant de- 

 sign. Large numbers of additional toll circuits were required and the 

 types of new telephone plant were such as to trend increasingly 

 toward the concentration of large numbers of telephone circuits on a 

 single route. This is illustrated best by the telephone cable, making 

 possible the installation of many hundreds of circuits along the same 

 route and in a smaller way by the application of carrier telephone 

 systems to open-wire lines, doubling or trebling the number of circuits 

 which could be carried by each such line. Satisfactory operation over 

 connections built up by switching together several toll circuits (multi- 

 switch connections as they are called) requires the insertion of trans- 

 mission gain at the switching points. Developments in methods of 

 providing such transmission gain by the proper manipulation of 

 repeaters were of such nature that increasing economies could be 

 realized by concentrating through switching as far as possible at a 

 small number of points. Also, this concentration could result in 

 operating economies. A General Toll Switching Plan lends itself 

 naturally to concentrations of circuits on important routes, and in the 

 development of the plan, account was taken of this trend. It there- 

 fore forms a background for realizing in future plant extensions the 

 maximum economies from these concentrations of route and of through 

 switching. 



These considerations led to the development in 1928 and 1929 of a 

 General Toll Switching Plan. The general features of this Plan may 

 be understood by referring to Figs. 22 and 23. Figure 22 shows how 

 the Plan applies within a given operating area such as an operating 

 unit of an Associate Company. Within such an area there were 

 selected a few important switching points and these were designated 

 as "primary outlets." Each toll center in the area is directly con- 

 nected to at least one primary outlet and each primar>' outlet is 

 directly connected to every other primary outlet in the area. There- 



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