TELEPHONE SYSTEM OF THE UNITED STATES 



91 



80 

 70 

 60 

 50 

 ■40 

 30 

 20 

 10 

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1898 1908 1918 1928 



Fig. 60 — Telephone conversations — Average number daily in millionsin United States. 



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Fig. 61 — -Average daily number of toll messages in the United States. 



