Carrier Telephony on High Voltage 

 Power Lines 



Bv W. V. WOLFE 



Introulctiun 



Till", use of |)()\ver from hydro-electric generating stations and 

 central steam ]>lants has increased until single companies serve 

 a territory of many thousands of s{|uare miles and the problem of 

 coordinating the distributing centers with the generating stations 

 has steadily increased in compIexit\-. 



One of the essentials of this coordination is obxiously an adequate 

 system of communication and until the recent advent of high frequency 

 telephony, this ser\'ice was secured over privately owned telephone 

 lines and over lines of public service telephone companies. 



The advent of the power line carrier telephone system now offers a 

 highly reliable and satisfactory means of communication in connection 

 with the operation of power systems. This equipment has been 

 designed to employ the power conductors as the transmission medium 

 and to provide service as reliable as the power lines themselves with 

 a low initial cost, a small maintenance charge, increased safety for 

 the operating personnel and transmission comparable in quality 

 and freedom from noise with that obtained on high grade commercial 

 toll circuits. 



Preliminarv Prohlems 



In proceeding with the development of the Western Electric Power 

 Line Carrier Telephone System three major problems were encount- 

 ered. It was first necessary to learn from field tests and close contact 

 with power companies tiie characteristics of power lines and asso- 

 ciated apparatus at high fretjuencies and the operating requirements 

 for such a telephone system; second, it was necessary to develop a 

 safe and efficient method for coupling the carrier ap|)aratus to the 

 power conductors and third, to select and dewlop circuits and i(iui[)- 

 ment suited to this .ser\ ice. 



The superiorit\- of the full-metallic over the grouiui return high 

 frefjuency circuit was easily established l)y comparati\e measure- 

 ments of attenuation, noise and interference, and therefore the experi- 

 intntal work was largely confined to the former circuit. 



