116 THE ELECTRIC TELEGRAPH. 



at whose ends are similar contacts, which press alternately 

 upon the anvils z' and c". The board is furnished with five 

 terminals for the reception of the outside wires. L is the 

 line terminal, R that to which the one side of the relay is 

 brought, the other side being to earth ; E the earth terminal, 

 and between c and z is inserted the line battery, only one 



Fig. 62. 



battery being required for reversals with this key. In the 

 fore part of the key, underneath the lever, is a spring, or 

 strip of brass, s, in permanent contact with L ; when the key 

 is at rest -this spring makes contact with a platinum point, 

 which is in permanent contact with the terminal R (relay) ; 

 a second point, underneath the spring, is in permanent 

 connection with the plate p of the commutator arrangement 

 just described. "When working the key the operator presses 

 the button E down into the knob d, and establishes contact 

 between s and p. Half-way between the upper and lower 

 contacts of s the spring meets with a small strip of metal in 

 connection with the earth, by which means, after working 

 the key, the line is discharged. The strip s is fastened to a 

 block, from which a pin presses upon a spring underneath, 

 reaching from the line terminal L, and keeping at the same 

 time the metallic strip s in connection with the line, and 

 holding the lever back upon the reposing contacts c , z . 



