222 MODERN ELECTRICAL INVENTIONS 



delphia. As long as the key K is pressed down, the coil M 

 acts as a magnet and attracts and holds fast the armature A. 

 But as soon as K is released, the current is broken, M loses 

 its magnetism, and the armature is pulled back by the spring 

 D. By a mechanical device, tape is drawn uniformly under 

 the light marker P attached to the armature. If K is closed 

 for but a short time, the armature is drawn down for but 

 a short interval, and the marker registers a dot on the tape T. 



FIG. 91. Diagram of the electric telegraph. 



If K is closed for a longer time, a short dash is made by the 

 marker. In general, the length of time that K is closed 

 determines the length of the marks recorded on the tape. 

 The telegraphic alphabet consists of dots and dashes and 

 their various combinations, and hence an interpretation of 

 the dot and dash symbols recorded on the tape is all that is 

 necessary for the receiving of a telegraphic message. 



The Morse telegraphic code, consisting of dots, dashes, and 

 spaces, is given in Figure 92. 



A H.... O. . U,._ 



-D ! -t -_ 



C.. . J . Q.._. W 



!)_ K__ R. .. X._. 



E. L_ S... Y.. ., 



F._. M__ T_ Z... . 



G__. N_. 



FIG. 92. The Morse telegraphic code. 



