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THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1952 



exemplified by the use of Fig. 5b rather than Fig. 5a. Although various 

 forms of all of the output leads were tested for efficient coml)ination only 

 the form used is shown for outputs other than the "0" and "1" leads. 



It is essential to scrutinize the final network for possible sneak paths. 

 Sometimes to avoid these sneak paths it is necessary to add one contact 

 on one relay to allow savings on others. Here again the inspection tech- 

 niques go hand in hand with switching algebra and the need for both is 

 obvious. The algebra obtains the various forms which are capable of 



B 



n 1 



RA E B DC 

 I h— I \—* X > I i f— l- 



— E A 



I X— •— — (- 



RAl "o" LEAD 



-X- 



Rf>' "7" LEAD 



P E " zo" LE AD 



X ~~ 



D RAl "," LEAD 



RAl "4.. LEAD 



"2" LEAD 



Fig. 6 — Combined translating circuit. 



different degrees of combination very quickly and efficiently. The inspec- 

 tion method is then necessary for the actual combination of these forms. 

 The additional RA relay contact is necessary to assist in avoiding in- 

 terconnections between the output leads until after the second pulse is 

 received. The final assignments of either .4 or B relay contacts are 

 chosen to equalize the load on these relays. 



THE COMPLETED CIRCUIT 



The final form of the counting and translating circuit is shown on 

 Fig. 7. The relays are all doul)le wound to gain the l)enefits of current 

 drain reduction. One additional advantage of using double windings is 

 the relay code reduction made possible since now only two codes are 

 necessary. One code serves the A relay and one other code serves the 



