252 



Common Science 



FIG. 142. Telegraphing across the room. 



to the free binding post of your telegraph instrument, and 

 press the key. Does the other instrument click? If not, 

 disconnect the ground wire and examine all connections. 

 Also press the sounder of each instrument down and see if 

 it springs back readily. It may be that some screw is too 

 tight, or too loose, or that a spring has come off; tinker 

 awhile and see if you cannot make the instrument work. 

 If you are unable to do so, ask for help. 



Figure 141 is a diagram of all the connections. 



When you want to telegraph, open the switch of the 

 instrument you want to send from and close the switch of 

 the instrument which is to receive the message. 



Holding the key down a little while, then letting it up, 

 makes a " dash," while letting it spring up instantly, makes 

 a " dot." 



Practice making dots and dashes. Telegraph the word 

 " cat," using the alphabet shown on the next page. Tele- 

 graph your own name ; your address. 



