MACHINE SiriTCIIlXG TELEPHONE SYSTEM 



69 



until the tripped brush engages the desired line or trunk. The 

 selector is then held in this position l>y a pawl associated with the 

 clutch. When the connection is to be taken down, the pawl is with- 

 drawn, and the selector is carried hack by means of the power drive 

 controlled by the clutch. When the selector reaches its normal posi- 

 tion the tripped brush is reset. 



Selectors used for different purposes are arranged to move their 

 brushes upward at different speeds. The speed most commonly 

 employed moves the brushes over the terminals at the rate of 60 



Brush Assemblv 



Fig. 12 — Sequence Switch Assembly 



trunks per second. At the top of the frame, just above the fifth 

 bank, are located commutators as shown in Fig. 11, one for each 

 selector. The multiple wiring of the brushes on the selector leads 

 to other brushes which move over strips on these commutators, and 

 thereby completes the connection from the movable selector to the 

 rest of the circuit, thus avoiding flexible wire connections with their 

 attendant troubles. This commutator, also, performs the more 

 important service of controlling the travel of the selector. Brushes 

 moving over conducting segments separated by insulation produce 



