INDUCTTIVE LOADING FOR TELEPHONE FACILITIES 151 



exchaYige area cable plant, and in leading to important service improve- 

 ments. 



As described, step by step, in the present story, coil loading has been a 

 very important factor in making possible the provision of satisfactory 

 telephone service at reasonable rates which have encouraged a continually 

 increasing use. Important elements in the public satisfaction to which 

 loading has made fundamental contributions are: (1) high-quality trans- 

 mission, and (2) high-speed service facilitated by the provision of relatively 

 large groups of relatively low-cost facilities. In the extensive utilization of 

 the long-distance service over repeatered, loaded, voice-frequency toll cable 

 facilities, loading must of course share the credit for the improved trans- 

 mission, plant cost-reduction, and speed of service with the telephone 

 repeaters and associated equalizing and regulating networks, where in- 

 volved. 



All of the coil loading development work for Bell System needs, including 

 the specific developments described in the present review, has been done 

 by Bell System people without outside aid. Coil loading was independently 

 invented by Dr. G. A. CampbelP of the headquarters staff of the American 

 Bell Telephone Company, and by Professor M. I. Pupin^ of Columbia 

 University, at nearly the same time, in 1899. The patent interference pro- 

 ceedings made necessary by the conflicting claims of the Pupin and Camp- 

 bell applications resulted in a priority award to Pupin during April 1904, 

 on the basis of a few days' earlier disclosure. The prompt purchase of Pupin's 

 rights in the invention before the interference action had gone far assured 

 the Telephone Company complete freedom to develop the new loading art 

 in the most advantageous ways. 



The improvements worked out and applied over the years are principally 

 due to groups of scientists and engineers working as teams on various phases 

 of the transmission research, development, and engmeering problems; on 

 the magnetic materials research and development problems; on the ap- 

 paratus-design and manufacturing problems; and on the field-construction 

 and traffic problems. Nearly all aspects of telephone systems' development 

 have been involved to a greater or less extent. 



In the aggregate, a large number of individuals have made important 

 contributions to the advancement of the loading art. The writer of this 

 review is to be regarded as a spokesman for his co-workers. Since the assign- 

 ment of a fair measure of personal credit to each individual who has been 

 involved would be extremely difficult, it is not attempted in the present 

 review. 



