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BELL SYSTEM TECHNICAL JOURNAL 



The primary outlets were selected after a careful study of the 

 present switching and operating conditions and the probable develop- 

 ment of toll traffic within the various areas with a view to obtaining 

 the minimum number of primary outlets capable of handling the 

 traffic economically. The routings provided by the plan are supple- 

 mented by direct circuits, or by other routings where the amount of 

 business justifies such additional circuits as indicated by the dashed 

 lines in Fig. 5. In general the requirement is made that these supple- 

 mentarv routes shall be at least as satisfactory, both as regards 



SOLID LINES - FUNDAMENTAL ROUTES OF 



GENERAL PLAN 



DASHED LINES - SUPPLEMENTARY DIRECT 



CIRCUIT GROUPS 



O PRIMARY OUTLET 

 • TOLL CENTER 



Fig. 5 — General toll switching plan — application in local company area. 



number of switches and transmission, as the routes provided by the 

 fundamental switching plan. However, when the supplementary 

 routes are used only as alternates to a primary routing they may be 

 somewhat less satisfactory in these respects. 



The tentative selection of primary outlets is shown in Fig. 7. It is 

 interesting to note that it is found practicable to take care of switching 

 for the 2,500 toll centers of the United States and eastern Canada 

 by the establishment of approximately 150 of these as primary outlets. 



For handling the business throughout the country eight of the 

 primary outlets are designated as regional centers, which are indicated 



