KEY COMMUTATOR. 



agent with as much facility and promptitude as ordinary written 

 or spoken language. 



128. In such forms of telegraph, the alternate suspension and 

 transmission of the current is produced by a commutator, which 

 has the form of the key of a pianoforte and is played upon in a 

 very similar manner by the agent who transmits the dispatch. 



One of the forms of these keys and the mechanism connected 

 with it, is represented in fig. 48. It is fixed upon a wooden block 



Fig. 4S. 



B . 



B B. The key plays upon a centre E. To the lower side of the 

 longer arm (E D) is attached a projecting piece of metal v, called 

 the HAiiitEE, under which is a fixed piece of metal of correspond- 

 ing form and magnitude called the AXVIL. 



The action of the key upon the current is the same precisely as 

 that already described (117) which is produced by the alternately 

 removing and restoring the hand to the contact piece in fig. 47. 

 The hammer in the present case represents the hand, and the anvil 

 the contact piece. One of the line-wires TO, is attached to the 

 anvil, and the other n to the metallic support E of the hammer 

 and key. When the hammer is in contact with the anvil, the 

 current passes, and when it is raised from that contact, the current 

 is suspended. 



The button D is faced with ivory to be pressed down by the 

 finger, and the screw d passing through the short arm of the key 

 is pressed upon the block x by the reaction of the spring r, when, 

 the key is not pressed down by the finger on D. The hammer v t 

 and anvil q are both faced with platinum to prevent oxydation, 

 which would obstruct that complete metallic contact which is 

 necessary to ensure the transmission of the current. 



An expert manipulator can work the key D with as much 

 celerity and correctness as can a performer on the pianoforte and 

 can express in that way in telegraphic language any dispatch 

 which is placed in manuscript before him, so as to transmit it to any 

 distant station. This will be explained more fully hereafter. 

 "When no dispatch is being transmitted from the station at which 



187 



