XATIONWIDE XUMHERIXG PLAN 853 



In many places local service areas were changed so that customers 

 could call into contiguous exchanges at local rates. To enable customers 

 to dial into these neary-by places the original numbering plans required 

 expansion to include this increased number of offices. In addition, with 

 the athance in the telephone art many cities introduced e(iuipment for 

 automatic charging on multi-unit and short haul toll calls so that cus- 

 tomers could dial such calls directly instead of placing them with an 

 operator for completion. In order to enable customers to dial these calls, 

 it was necessary to expand the original city numbering plans to encom- 

 pass wider and wider geographical areas. 



In expanding the various types of numbering plans to serve a larger 

 nimiber of central offices than were originally anticipated, various ex- 

 pedients were resorted to. In the largest cities having three-letter office 

 codes a numeral was substituted for the third letter thus \ery materially 

 increasing the code capacity from about 325 to about 500 and making it 

 possible to form a number of codes using the same office name. The name 

 CAXal for example, instead of serving but one office may ser^'e a number 

 of offices, CAnal 2, CAnal 3, CAnal 4, etc. In the medium size cities 

 ha\'ing two-letter codes, expansion meant adding a digit to the code to 

 all or in some cases to only a part of the offices in the city. 



The fi\'e-digit places Avere usually expanded by adding a digit to 

 some of the numbers so that some of the telephones had five digits and 

 others six digits in their numbers. 



As a result of choosing originally a numbering plan which at the time 

 seemed adequate and most suitable for the city involved and in many 

 cases being forced to expand to meet changing needs, we now have in the 

 Bell System a considerable variety of different numbering plans. These 

 are given in Table I. The numbering plans given are all adequate to 

 serve the present local dialing needs for the cities in which they appear. 



Having reviewed the numbering plan situation as it exists today in 

 the \-arious cities and towns, let us turn to the problem of handling toll 

 calls. Under ringdown operation there is an operator at the outward toll 

 center where the call originates and another operator at the terminating 

 or inward toll center. On built-up toll connections there are additional 

 operators at each intermediate toll switching point. The inward toll 

 operators, who are familiar with the numbering plans in the offices served 

 by their particular toll center, can be relied upon to connect to the de- 

 sired station even though there is uncertainty on the part of the calling 

 customer or the outward toll operator regarding the precise pronuncia- 

 tion or spelling of the name of the called office or the particular form of 

 numbering system used at the called city. 



