TELEPHONE SYSTEM OF THE UNITED STATES 7 



pole lines and many other very important parts of the telephone 

 plant. The engineering of the additions to the Bell Telephone System, 

 now aggregating over 500 million dollars a year is, therefore, neces- 

 sarily based on careful forecasts of the amount and type of business 

 to be expected for a number of years in the future and good engineer- 

 ing judgment must be applied in determining the types, quantities 

 and design of plant. These must take into account not only the 

 expected amount of service required but also expected future changes 

 in the character and standards of service demanded and in the appa- 

 ratus and materials expected to become available. In view of the 

 capital expended in extensions and the large amount of plant already 

 in service, the engineering work involved is considerable. There are 

 now approximately 10,000 engineers engaged in the work of the Bell 

 System of which approximately 6,300 are in the operating companies, 

 2,200 in the headquarters departments and 1,500 in the Western 

 Electric Company. These figures apply to men doing work of engi- 

 neering grade, and inclusion of assistants of all kinds, stenographical, 

 clerical, laboratory, etc., would more than double these figures. 



Local Service 



General 



Service within the limits of a single telephone exchange is spoken 

 of as local service. This generally includes service within a large met- 

 ropolitan area, a city with its surrounding suburbs or a town or village. 

 During 1928 customers of the Bell System originated approximately 

 24,000 million local calls of which approximately 19,000 million 

 originated from manual and 5,000 million from dial telephones. This 

 represents an average daily usage of approximately 5.5 calls per 

 telephone station per day. 



The speed of service is illustrated by the following average figures. 

 In the smaller cities with manual operation where the operator who 

 takes the call completes it herself without trunking, the average time 

 from the start of the call to the answer of the called station is 19 

 seconds. The corresponding figure for manual calls in large cities 

 based on about three million observations made in the year 1928 in 

 38 large cities of the country is 28.8 seconds. The same observations 

 indicate that when fully converted to the dial system the speed of 

 service in the large cities will be about 22.5 seconds. 



As to the accuracy of service, 98 per cent of all calls are handled 

 without error. The most serious errors are those resulting in wrong 

 numbers. The mistakes made by the subscribers and equipment 



