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BELL SYSTEM TECHNICAL JOURNAL 



chanically, so that that set will contact successively over terminals 

 as the selector rises. 



A friction clutch is provided at the base of each selector, so arranged 

 that the selector can be raised or lowered by power supplied by a 

 constantly rotating small motor, common to 60 selectors. A magnet 

 is also provided for tripping, by means of a rotating rod, any one of 





Fig. 11 — Commutator for Controlling Vertical Movement of Selecting A'lechanism 



the five sets of brushes into mechanical engagement with the terminals. 

 In choosing a trunk or line, that one of the five sets of brushes which 

 has access to the panel in which the desired trunk or line happens 

 to be, is tripped so that it makes contact with the bank terminals 

 before it. The selector then moves upward, under the proper control, 



