4°4 



POPULAR SCIENCE MONTHLY 



NOTES ON THE DEVELOPMENT OF TELEPHONE SEEVICE 



By FRED DE LAM) 

 Pittsburg, Pa. 



r N November, 1876, Graham Bell perceived the value and efficiency of 

 -*- the metallic circuit and advised its adoption for telephone service 

 to overcome the inductive annoyances. On February 1, 1878, the 

 parent Bell company recommended the use of metallic circuits for 



GROUND 



LINE 



Fig. 30. 



exchange service, although only three telephone companies had ex- 

 changes in operation that month. But many of the local companies 

 could only perceive that the introduction of a metallic-circuit system 

 meant double the cross-arm space, stronger poles, double the terminal 



