TRENDS IN PRACTISE AS AFFECTING COORDINATION 181 



monic components which were present in apparatus wave shape and as 

 to the relative effect of these components when appearing in communi- 

 cation circuits by induction from power circuits. As a result of this 

 study an instrument was developed for measuring "Telephone Inter- 

 ference Factor" of a voltage wave. With this instrument as an aid 

 a better understanding of the bearing of wave shape has been gained 

 by the apparatus manufacturers and there has resulted a gradual 

 improvement in the wave shape of new apparatus. 



It is recognized that there is a median line beyond which general 

 improvement in the inherent wave shape of apparatus would not justify 

 the attendant increased difficulties of design and increased manufac- 

 turing costs, — to avoid the alternative of applying in specific cases, 

 available and less expensive methods of externally correcting wave 

 shape. Work is now in progress cooperatively between the manufac- 

 turers and users looking toward the establishing of a measure of wave 

 shape in apparatus design which will strike an economic balance be- 

 tween benefits and burdens. 



The increasing use of rectifiers for conversion from alternating to 

 direct current has an influence on inductive coordination. Consider- 

 able study has been devoted to this matter as result of which methods 

 for control of the distortion of the d-c. voltage wave caused by the 

 rectifiers have been applied in several instances and a solution of this 

 part of the problem appears to be in hand. More study and experience 

 are needed as regards the specific conditions under which the wave 

 shape distortion of the alternating current supply would require con- 

 sideration. 



With the progress begin accomplished in the design and application 

 of apparatus and the better understanding of the influence of circuit 

 and transformer connections on inductive relations, problems concerned 

 with wave shape can be expected to steadily decrease. The status 

 of the cooperative study of this subject is described in this symposium. 



Conclusion 



A brief outline has been given here of the general trends in plant 

 development and operating practise in telephone and power systems 

 with special regard to those trends which affect the problem of coordin- 

 ation. While naturally there have been influences working favorably 

 and others working unfavorably toward the problem it is clear that the 

 preponderant effect of the development now being applied in the two 

 industries is reducing the proportion of new situations in which specific 

 coordinative measures are necessary. While to a considerable extent, 

 as indicated in the body of the paper, this is due to the natural trends 



