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BELL SYSTEM TECHNICAL JOURNAL 



impulses which, when sent back to the sender, indicate to it the exact 

 position of the selecting mechanism. 



Sequence Switch. Another device of great importance is the 

 "sequence switch," shown in detail in Fig. 12. It is operated through 



Fig. 13 — Selector Frame Completely Equipped 



an electromagnetic clutch from the same motor that drives the 

 selectors. 



The sequence switch may be described as a circuit controller or 

 device whose function is to establish in a definite sequence such circuit 



