ECONOMICS OF TELEPHOXK RELAY APPLICATIONS 



2.')! 



wp wR ' 



(31) 



The expression may be evaluated wlien a relation between / and circuit 

 resistance R is established, usually a matter for experiment in any given 

 case. 



Illustration 



For a pai'ticular case let us assume that p = O.OOOG, so that equation 

 (31) is 



C = l f 1670 i c^t + ^4' 

 w \ g R 



Tj^pical values of operate time, t, for a speed relay in 50- volt telephone 

 applications are given in Table III. From this information, one may 

 readily evaluate equation (32) to cover the practical range of conditions 

 that are met in seri-ice. This has been done, in Fig. 16, to give the total 



(32) 



200 400 600 800 1000 



COIL RESISTANCE, R, IN OHMS 



15 Optimizing costs of speed plus power by relay coil design. 



