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BELL SYSTEM TECHNICAL JOURNAL 



stations have increased 88 per cent and customers of central stations 127 

 per cent. The leaders of both utilities confidently expect that, apart 

 from temporary setbacks a.ssociated with recessions in general business, 

 the recent rapid growth of these utilities will continue throughout the 

 next decade. 



- 80 

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1 



1930 Population 123,900,000 



Telephone messages 21,600,000,000 



Kw. hours generated 90,000,000,000 



Fig. 1 — Per cent increase, 1920 to 1930, in population and in telephone and 



power usage. 



Note: Values for 1930 are estimates based on best available data. Telephone 

 data refer to Bell System. 



Such a rapid growth of the two utilities both of which must supply 

 the same customers with services essential to their comfort and pros- 

 perity, necessarily brings with it a large number of cases of physical 

 proximity between the plants of the two utilities where, due to the 

 widely different characteristics of the circuits involved, difficulties may 

 arise. The necessity for active study of the coordination of the differ- 

 ent systems and for the current handling of large numbers of individual 

 situations will continue for a long time to come. 



Associated with this rapid growth there has been another trend in 

 these two utilities which has an important effect on coordination work. 



