Status of Joint Development and Research on Noise 

 Frequency Induction * 



By H. L. WILLS and O. B. BLACKWELL 



The work of finding out the technical facts bearing on the problems of the 

 physical relations of power and telephone circuits was intrusted to the Joint 

 Subcommittee on Development and Research of the National Electric 

 Light Association and the Bell System. This paper has to do with this fact- 

 finding work so far as it concerns noise frequency induction. 



The work on inductive coordination may be classified into three groups of 

 factors: 



L Influence factors which concern the characteristics of the power 

 circuits. 



2. Susceptiveness factors which concern the characteristics of the 



communication circuits. 



3. Coupling factors which concern the interrelation of power and 



communication circuits. 

 The paper discusses these various factors in detail and describes the work 

 done by the committee or in progress regarding them. References are given 

 to published reports and papers which present the results of technical 

 studies already completed. 



Many of the existing noise frequency induction problems have arisen 

 because of the development of the art of the two industries without such 

 close cooperation between them as now exists. It is becoming evident, from 

 the work of this Joint Subcommittee, that while it is not practicable to 

 design machinery and apparatus for power systems to be entirely free of 

 harmonics, or to ideally balance either power or telephone circuits, it is 

 possible to control these factors within limits which, in conjunction with 

 the control of coupling obtainable by cooperative planning of routes and 

 coordination of transpositions, permit satisfactory operation of both 

 services without unduly burdening either. 



T 



^HE Joint Subcommittee on Development and Research is the 



agency through which the National Electric Light Association 



and the Bell Telephone System carry out technical work on problems of 



physical relations which vitally affect their respective growth and 



operating practises. In the present paper and companion papers the 



status of this joint development and research work is described. 



The present paper, Part II of the Symposium, is concerned with 



problems of induction in telephone circuits under normal operating 



conditions of power systems which results in noise. Part III of the 



Symposium treats of induction at the power system fundamental 



frequency, principally that occurring at the time of grounds, short 



circuits or other abnormal conditions of power systems. Part IV of 



the Symposium treats of the physical relations and of the special noise- 



* Part II of the Symposium on Coordination of Power and Telephone Plant. 

 Presented at the Winter Convention of the A. I. E. E., New York, N. Y., January 

 26-30, 1931. Published in abridged form in Electrical Engineering, April, 1931. 



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