THE ELECTRIC BURGLAR-ALABM. 



61 



jar. Four of these elements put up in a wooden case constitute the 

 battery usually furnished. 



These appliances provided, the most common way of using the 

 system is to make it complete in each building, the alarm apparatus 

 being placed in a sleeping-apartment in a private house, and in the 



Fig. 3. 



watchman's room in a place of business. So arranged, the condition 

 of the circuit is this : In the daytime, when the doors and windows are 

 open, the circuit is continuous at all points except at the alarm appara- 

 tus. At night this is reversed, the circuit being closed at the instru- 

 ment, and broken at all the points protected, A movement at any of 

 these points which closes the circuit gives the alarm and turns the 

 proper needle on the annunciator. The connection with the alarm is 

 made at night by an attendant, and broken at any desired time in the 

 morning. In private houses fitted with electric bells, a clock is often 

 provided that disconnects the alarm in the morning and turns the cur- 

 rent on to a bell placed in the servants' room. The movement by 

 which this is done is something similar to that of the ordinary alarm- 

 clock. 



The protection afforded with such an apparatus in good working 

 order is probably as perfect as it can be made. It is generally impos- 

 sible to cut the wires from the outside of the building, and unless this 

 is done intrusion will start the alarm. Even if the wires be cut, but- 



