Nationwide Numbering Plan

In telephone language a numbering plan gives each telephone in a city, a town, or a geographical area an identity 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 teas realized that an improvement in the method of dialing toll calls to distant cities was essential in order to realize the maximum 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 operator, 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. Ultimately each central office will be given a type of number consisting of an office name and five numerical digits, such as LOcust 4-5678, in which the first two letters of the office name become the two letters of the central office code.