Uses of Electromagnets 219 



the combinations of dots and dashes used in the American Morse 

 code to represent letters: 



A B C D 



E F G H 



I J K L 



M N O P 



Q R S T 



U V W X 



Y Z 1 2 



7890 

 A simple telegraph can be made from a battery, a sending 

 key, a sounder, and a connecting wire. A second wire is not 

 necessary to complete the circuit if the battery on the sending end 

 and the sounder on the receiving end are connected by wires to 

 the ground, which acts as a conductor. When the key of the 

 sending set is pressed, the circuit is completed and a current of 

 electricity at once flows from the battery, through the wire, to 

 the sounder. The sounder consists of an upright electromagnet 

 near the ends of which is a soft iron armature connected to a 

 brass rod. With the circuit completed, the electromagnet attracts 

 the armature downward, pulling the brass rod against a screw, 

 making a click. When the key is released and the circuit broken, 

 the armature is pulled upward by a spring and the brass rod 

 clicks against another screw. In this way every movement of 

 the key produces a click from the sounder. By varying the inter- 

 vals between clicks, the dots and dashes of the Morse code can be 

 given. 



