Nationwide Numbering Plan 



By W. 11. NUNN 



(Manuscript received May 15, 1952) 



In telephone language a numbering plan gives each telephone in a city, 

 a town, or a geographical area an identify or designation different from 

 that given any other telephone in the same area. There is a wide variation 

 in the types of numbering arrangements in use today in the Bell System, 

 and this paper gives the reasons for this diversity, and examples of the 

 various numbering plans now in use. With the introduction of modern toll 

 switching facilities and the extension of toll dialing to nationwide scope, 

 it ivas realized that an improvement in the method of dialing toll calls to 

 distant cities, was essential in order to realize the inaximum speed and 

 accuracy inherent in toll dialing. A nationwide numbering plan covering the 

 United States and Canada has been designed. Each of the more than 20,000 

 central offices in the two countries are to be given a distinctive designation 

 which identifies that particular office. This designation is to consist of a 

 regional or area code and a central office code The new switching equipment 

 for the key points in the toll network is being designed so that any toll opera- 

 tor, wherever located, will use the same designation or code for reaching a 

 given office. The combination involved in laying out these areas and the 

 composition of the area codes are presented. A total of 152 codes are available 

 of which approximately 90 are assigned to the present numbering plan areas. 

 Ulfimafrly each central office will be given a type of number consisting 

 of an office name and five numerical digits, such as LOcust 4-6678, in 

 which the first two letters of the office name become the two letters of the 

 central office code. The entire program will take a considerable number of 

 years to realize, but is one which must be accomplished in order to achieve 

 the best residts in operator toll dialing and the ultimate goal of nationwide 

 customer toll dialing. 



In telephone langnage a numbering plan is exactly what the name im- 

 plies, a plan or system of giving each telephone in a city, a town or any 

 geographical area an identity or designation which is different from that 

 given every other telephone in this same area. This designation is the 



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