The Bell System Technical Journal 



January, 1930 



Telephone Communication System of the United States ^ 



By BANCROFT GHERARDI and F. B. JEWETT 



This paper presents the results which have been obtained up to the 

 present time in developing telephone communication in the United States 

 of America, this development having been worked out in a form to meet the 

 particular conditions which present themselves in that country. The paper 

 first deals with a brief description of the general structure and organization 

 of the telephone communication system giving the organization of the 

 Bell System which handles the greater part of the telephone service of 

 the country and the reasons for and advantages of this organization. _ In 

 this connection some figures are presented with respect to the technical 

 personnel who are continuously engaged in studies to develop the art and 

 to provide new methods and facilities for improving the service. 



Local service, that is the service within the limits of a single telephone 

 exchange area, is next discussed. Figures are given with respect to the vol- 

 umes of telephone calls handled in the Bell System, the speed with which 

 the connections for these calls are completed and the operating force re- 

 quired. Reference is also made to the standards of transmission given 

 and the various problems encountered in meeting these standards. Figures 

 are given with respect to station growth, to the increased efficiency of sta- 

 tion apparatus and to the improvement in types of instruments. Various 

 types of private branch exchanges provided to meet the needs of customers 

 using a large amount of telephone service are discussed. The cable plant 

 is considered mainly from the construction standpoint and typical illus- 

 trations are given of some of the construction practices. The various 

 types of central office switcning systems in common use are described, 

 including magneto, common battery and dial systems, the latter including 

 both the step-by-step and panel systems which ate being provided in 

 increasing amounts in the Bell System. The subject of buildings to house 

 these various equipments as well as the operating forces and headquarters 

 staffs in many cases is briefly discussed, also standardized layouts and 

 floor plans. The problem of giving telephone service in the rural com- 

 munities, which is a very important one in the telephone development 

 in the United States, is also biiefly treated. 



The toll service is considered, first with respect to the shorter haul toll 

 business and the problems involved and then with lespect to the long 

 distance toll service. Figures are given showing the speed of service and 

 the amount of traffic handled. For the short distance toll service, two 

 important methods of handling tne business are described, namely, manual 

 straightforward tandem and dial tandem. 



The long distance service, which has developed most rapidly in recent 

 years, is described in some detail in the paper. Among the important 

 features of this service is noted the recently developed method of com- 

 pleting toll calls with sufficient speed so that on most of the calls the calling 

 subscriber remains at the telephone. The various types of toll circuits 

 are described including open wire circuits operated both at voice frequencies 

 and by carrier systems and long toll cable circuits. The operation of 

 these long circuits requires a large number of repeaters in tandem and 

 the design and maintenance problems which this arrangement requires 

 are pointed out in the paper. 



1 Presented by Dr. F. B. Jewett before the World Engineering Congress, Tokio 

 Japan, October, 1929. 



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