Machine Switching Telephone System for 

 Large Metropolitan Areas 



By E. B. CRAFT, L. F. MOREHOUSE and H. P. CHARLESWORTH 



Synopsis: From the earliest forms of telephone switchboards to the 

 modern types, the development of the switchboard has been marked by the 

 increasing use of automatic methods to supplement the manual operation 

 wherever this would result in better service to the public or more efficient 

 operation. 



In addition to all that has been done in developing and introducing auto- 

 matic operations with manual switchboards, it has been found desirable and 

 practicable to go further in the direction of introducing automatic opera- 

 tion in the telephone plant and a machine switching system has been 

 developed in which the bulk of the connections are established without the 

 aid of an operator. 



The complexity of a large metropolitan area and the exacting requirements 

 which a machine switching system must meet are outlined briefly, and the 

 system which has been developed to meet these requirements is described. 



The application of the system to a typical large metropolitan area and the 

 means provided for permitting its gradual introduction into the existing 

 plant are discussed. 



IT is the purpose of this paper to outline briefly certain important 

 developments in connection with machine switching telephone 

 systems and to discuss the application of the results of these develop- 

 ments to the problem of providing telephone service in large metro- 

 politan areas. 



The telephone was invented in 1876. Almost immediately there- 

 after it was recognized that, for it to attain its greatest field of use- 

 fulness, switchboards and switching centers would have to be estab- 

 lished for effecting interconnection between subscriber's lines. 



Professor Bell's vision of the future was given in a statement to 

 prospective investors. He said : 



"It is conceivable that cables of telephone wires could be laid 

 underground, or suspended overhead, communicating by branch 

 wires with private dwellings, country houses, shops, manufac- 

 tories, etc., etc. — uniting them through the main cable with a 

 central office where the wires could be connected as desired, 

 establishing direct communication between any two places in the 

 city. Such a plan as this, though impracticable at the present 

 moment, will, I firmly believe, be the outcome of the introduction 

 of the telephone to the public. Not only so, but I believe in the 

 tuture wires will unite the head offices in different cities, and a 



Presented at the Midwinter Convention of the A. I. E. E., New York, N. Y.. 

 February 14-17, 1923. Published in the Journal of A. I. E. E. April, 1923. 



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