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BELL SYSTEM TECHNICAL JOURNAL 



equipment for 10,000 lines. These offices and the associated plant 

 provide for intercommunication between 1,400,000 telephones, and 

 approximately two trillion possible connections. It is estimated 

 that by the year 1940 there will be 300 central office switchboards 

 within the New York Metropolitan area, serving some 3,300,000 tele- 

 phones — or nearly two and a half times the present number. 



NEW J E R S E 



Fig. 3 — Map Showing Location of Central Offices in New York Metropolitan Area 



Manual Switchboards 



The system most commonly employed today for connecting sub- 

 scribers' lines together is the so-called "manual" system; that is, a 

 system in which operators are employed to make the actual connec- 

 tions between subscribers' lines, although so many of the functions 

 are performed automatically that, except in name, it is to a large 

 degree automatic. 



It is a long step from the early switchboards to the modern common 

 battery multiple manual switchboards. The history of the develop- 

 ment of switchboard equipment and apparatus shows that enormous 

 progress has been made in this art in a comparatively few years. 

 As the telephone subscribers have grown in number and as the amount 

 and complexity of the traffic have increased, it has been only by the 

 most intensive development that it has been possible to keep ahead of 

 the demand for telephone service, and that telephone engineers have 

 been able to get the speed, efficiency and accuracy that are obtained 



