General Toll Switching Plan 



The technical developments which are outlined in the preceding 

 sections of this account made possible continued improvement in the 

 range and quality of telephone conversations over long distances and 

 economies in the costs of providing long distance circuits. As a result, 

 long distance telephone service grew rapidly, both in volume and in 

 extent, and by 1915 service was established between the Atlantic and 

 the Pacific Coasts. The application of technical developments 

 continued, increasing the transmission efficiency not only of the very 

 long telephone circuits which technical developments have recently 

 made possible but also of shorter toll circuits of all lengths. 



Although the opening of the transcontinental line showed the pos- 

 sibility of establishing direct telephone service between any two points 

 in the country, a great deal more had to be done in order to closely 

 realize the Bell System ideal of universal service, that is, good service 

 between any two points in the country. While a large proportion of 

 the toll board messages (at present 80 per cent) is handled by direct 

 circuits between the two terminal points, there is naturally a very 

 large number of combinations of cities and towns in the country 

 between which the telephone business is too light to justify direct 

 circuits — in fact, these constitute a large percentage of all the combi- 

 nations of places in the country. For these conditions, when a 

 telephone connection is required, it must be established by switching 

 together two or more telephone circuits. Some cases might require 

 switching together a considerable number of telephone circuits, this 

 sometimes involving difficulty and delay in establishing the connection. 

 Also, while the telephone circuits may be so designed that, individually 

 or in combinations of two, they provide very satisfactory transmission, 

 in some of these cases requiring a number of switches, the combination 

 of circuits might result in unsatisfactory transmission. 



In order that universal service for the nation might practically be 

 realized, it was necessary to provide an underlying plan for the routing 

 of telephone calls between any two places such that the maximum 

 number of switches necessary for building up the connection would be 

 as low as practicable. This must apply to connections between any 

 two points in an operating area, or other natural subdivision of the 

 country, and also to the country as a whole. Furthermore, the plan 

 should provide for a transmission design of toll circuits such that 

 transmission conditions will be satisfactory on individual circuits when 

 used for direct traffic between their terminals, and also for any combi- 

 nation of circuits which may be connected together in establishing a 



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