HISTORY AND PROGRESS. 



When at rest the tongue leans against the agate point, 

 and the local circuit is open ; but when a current circulates 

 in the line and coils of the electro -magnet the armature is 

 attracted towards the poles, and the tongue strikes against 



Fig. 47. 



the point of the contact-screw h d, and closes the local 

 circuit, the current of which passes from /' (#, b, d, i, k, g) 

 to I". 



64. Simple Morse Embosser for two Stations with Relay. 

 Fig 48. represents a plan of connection of a Morse embosser 

 with relays and local batteries for two stations. G is the 

 line galvanoscope connected, on the one side, with the line, 

 on the other, with the lever of the key K. Its purpose is to 

 show the presence of current in the line, and to give a rough 

 idea of its strength. The front or working contact 1 of the 

 key is connected with the pole c of the line-battery B, and 

 the other pole z with the earth-plate. The back, or reposing 

 contact, of the key is connected with one end of the electro- 

 magnet coils of the relay R, the other end being in commu- 

 nication with the earth-plate. Lastly, between the contact- 

 point 2 of the relay and its tongue or armature are inserted 

 the coils of the Morse M and the local battery L B. 



When in repose the levers of both keys are on the contacts 

 2, and the line, therefore, at both ends to earth through the 

 coils of the relays. On pressing down either of the keys 



