SYNCHRONISING MECHANISM 



the relay, exciting the coils and causing the 

 small magnetised armature to be attracted to- 

 wards the left side in the diagram. The pla- 

 tinum contacts XX then touch, and current from 

 the local battery passes through the magnet Z. 

 This attracts the armature H, so that the check turns 

 about the fulcrum F into a position such that T 

 is free to move and the drum consequently again 

 starts running. 



The motive me- 

 chanism driving the 

 drum cannot of 

 course stop and 

 start abruptly at the 

 end of each revolu- 

 tion, a friction 



clutch is therefore 



u 

 provided, as shown 



in the next diagram (Fig. 19). The shaft is 

 cut through and two parallel faces FF fitted, 

 springs SS being attached to the lower one which 

 grip the upper one. When the motion of the 

 cylinder is checked, the two faces turn one against 

 the other. The springs are fixed to a collar C 

 which can be screwed over the threaded shaft, 

 K being a lock nut. The tension of the friction 

 clutch can thus be regulated. 



The transmitting cylinder is, as 'already stated, 

 revolved at about the rate of one revolution in five 



FlG - 



