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THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1954 



and the sum of this equation and that for lot size represents the system 

 cost for any one condition. 



Fig. 13 shows this variation for an assumed case for which 



iV = 500,000 parts per year. 



A; = 0.15. 



S = $100. 



C\ 



A 



0.20 for spring set cost. 

 0.005 for spare spring cost. 



0. 



Here it is found that the greatest benefit comes from using in the neigh- 

 borhood of six kinds of spring sets. It is further clearly seen that the sys- 

 tem as a whole will not be particularly penalized if the number of sets 

 chosen is a few different from this quantity — but a penalty of almost 

 two cents per relay, or about two thousand doUlars per year would be 

 incurred by erring too far toward the extreme. 



Part IV — Choice of Special Adjustment for Maximum 

 Speed Economy 



Speed can be an exceedingly valuable property of a relay, as shown 

 in Section 1.4. There are cases for example where every saving of 1 



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NUMBER OF KINDS OF SPRING SETS. V 



Fig. 13 — Optimum number of spring sets. 



