52 Electric Five Alarms. 



Before describing any of the methods by which this can 

 be accomplished, it will be as well to consider the necessary 

 conditions that are required for an efficient system. It should 

 be simple in construction ; not liable to get out of order ; 

 certain in its action ; be capable of transmitting its signals 

 automatically — that is to say, it must not require any com- 

 plicated instructions to be carried out by the person giving 

 the alarm, for we must imagine that such person might be 

 in a state of excitement, and could not, therefore, be 

 depended upon to read or execute anything but a very simple 

 direction. 



The receiving mechanism must be reliable, and consist of 

 audible and either a visual or recording alarm. If audible 

 alone, the same signal must be repeated at short intervals, to 

 ensure its correctness being verified. 



There is very little doubt that America possesses the most 

 extensive and perfect system. One of the earliest forms is 

 still in use there, and works satisfactorily. 



The city or town is divided into blocks, each known by a 

 number ; at a suitable place in each block is fixed a small 

 wooden or iron case, having a door secured by a lock. On 

 this door is painted the number of the block, and instructions 

 where to obtain the key. There are three or more keys to 

 each case, one being left at the nearest hotel, one at a 

 chemist's or other suitable store, and one with the policeman 

 on duty. In case of fire breaking out in any block, the 

 person who wishes to give an alarm, after obtaining the key, 

 opens the door of the case. Inside is to be seen a ring 

 attached to a chain, with the simple instruction of " Pull." 

 The ingenious part of the mechanism now comes into play. 

 Irrespective of the chain being pulled either quickly or 

 slowly, to its full length or only for a short distance, if it 

 be held in the hand or let go, the signal is transmitted with 

 the same certainty and regularity. Pulling the chain down 

 raises a small lever with a weight on it that is instantly 

 released ; this starts a train of wheel- work which in 

 rotating closes and breaks an electric circuit, transmitting 

 signals something like the Morse code. 



At the receiving station these signals come in the form of 

 strokes at irregular intervals on a large bell ; at the same 

 time a Morse register is started, and the signals recorded on 

 the tape in the ordinary way. These signals are repeated 

 three or four times, the sending wheel being arranged for 

 that purpose. With the exception of a somewhat expensive 



