140 



THE ELECTRIC TELEGRAPH. 



a positive current enters the line L 2 as follows : 4- K, 3, H t , 

 S 2 , /, L 2 , opposite station apparatus, earth + K. 



It is therefore evident that the printing instrument will 

 translate any signals it may receive to the next station. 

 As there is no communication between the line and the 



Fig. 78. 



point s l9 the discharge current does not pass through the 

 relay. Suppose now the relay G 2 placed in circuit for recep- 

 tion of signals, by transferring the switch from s 2 to s lf the 

 arm I, in going over, rubs against the earth contact s 3 , and 

 consequently the line will be discharged before being con- 

 nected with the relay. 



At the back of the apparatus, the axis supporting the 

 releasing lever carries also a commutating beam, which, when 

 at rest, makes contact with s l9 in connection with the relay ; 

 but when the armature of the small electro-magnet is 

 attracted, the commutating lever makes contact at the point 

 s 2 , in communication with the printing lever. The discharge 

 of the line is effected by means of the boot T, Fig. 77. This 

 boot is insulated at the toe and heel, but not in the middle 

 of the sole, so that either in a state of repose or when dancing, 

 no electrical connection exits between the boot, that is to say, 



