1 877.] 
375 
Recent Advances in Telegraphy . 
it, and breaking contact with h while making contact with a. 
This, while keeping the eletftro-magnet A still in circuit, also 
puts the magnet B in circuit. In this way the electro- 
magnet B is alternately thrown in and out of circuit, and 
the effect of this on the reed is to keep up its vibration. 
The reed, thus kept vibrating by the electro-magnets and 
local battery, is used to interrupt the line circuit and sending 
current. The sending battery is connected up, as shown, 
through the signalling-key to the reed, and by the reed- 
