252 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1954 



Table III — Typical Values of Operate Time 



cost penalty for the case of very short holding time (h = 100 hr. per 

 year) and for long holding time (h = 2000 hr. per year). The optimum 

 coil resistances for these cases are seen to lie between 200 and 400 ohms 

 for the long holding time condition, and to be as low as possible for the 

 case of short holding time. As a result we see an appreciable economic 

 incentive to plan relay designs which are capable of operating on low 

 resistances. Further study of heat dissipation, operation with holding 

 windings, contacts to withstand heavy currents, and other de^dces to 

 gain fast action, therefore take on added importance to the relay de- 



signer. 



Part VI — Choice of the Actual Code 



With the background of the previous sections, the systems designer 

 can now decide what codes he needs to use in his circuits so as to be 



< 35 



Fig. 16 



200 400 600 800 1000 



COIL RESISTANCE, R, IN OHMS 



Best coil design for both speed and power economy. 



