CHAP. III.] 



ELECTRIC TELEGRAPHY. 



563 



We will describe the indicator first. 



Fig. 361 represents the outside appearance. It is a box provided 

 with a dial, having the same divisions as the dial of the manipulator. 

 In the interior some clockwork is fixed, whose escapement wheel and 

 the needle of the dial are on the same axis, so that each time a tooth 

 of that wheel passes, the needle moves over one division. The 

 current sent through the line by the manipulator of the sending 

 station arrives at one of the binding screws-, seen at the base -of the 

 indicator, passes along the wire of the bobbins of an electro-magnet 



FIG. 362. Breguet's indicator, view of the mechanism. 



placed in the inside and base of the indicator, acts on a peculiar 

 mechanism we will presently describe, and passes to the earth through 

 the other binding screw. We have to show further what is the 

 method of the current's and the electro-magnet's action on the escape- 

 ment wheel, in order to complete the explanation of the way in which 

 the signals, letters, or figures sent, are reproduced on the dial by 

 means of the needles, this is rendered easy by the study of Figs. 362 

 and 363, which represent the special mechanism of the receiving 



