/e/:7../)".v i.\ I III-: niii.i. sysriiM 



29 



with ilii- coiit.irl r.irryiiiji; s|)ri^l;^.. Main' ol tlio switrliin^; opi-r.i- 

 tioiis recjuirwl for n-Liyinj' a ciri-iiit from point to point throuj^h an 

 office can ho pi-rforinctl uiulcr conditions allowing greater latitude in 

 relay desiijn which has led to tin- dexelopment of se\'eral interesting 

 and iiiuistial forms of nuMli-contact rela\s in which the armatures 



Fii:. 20— tall indicatnr polar relay 



indirecth' control grcnips of contact carrying springs. In llic (lc\elop- 

 ment of the machine switching system the work of establishing cir- 

 cuits performed by human relays was transferred to mechanical 

 relays and it soon became evident that the number of individual 

 relay structures of the conventional type required for such a sub- 

 stitution would be so great and the circuit arrangements would be 

 so coinplicated that the cost would be prohibitive. 



The 24 cam sequence switch shown in Fig. 21 is an interesting 

 example of the remote contact control multi-contact relay that not 

 only performs the functions of a multitude of individual relays but 

 actually replaces entire circuits which would require large numbers 

 of relays to control the particular relays that transferred the circuit 

 from point to point. The relay sequence switch shown in the figure 

 is assembled with a shaft that may be rotated into any one of 18 

 positions which are stamped on an index wheel and are indicated by 

 the position of the wheel with reference to a pointer fixed to the frame 



