Popular Science Monthly 



947 



The Construction of an Automatic 

 Battery Circuit-Breaker 



AN automatic circuit-breaker and its 

 L operation are depicted in the ac- 

 companying diagrams. 



Referring to Fig. I,^ is a wooden base 

 4 ins. by 2 ins. by j^ in., 5 is a brass 

 strip }/s in. by }i in., bent as shown so 

 as to stand 2^i ins. above the base. 

 The magnet M is 2)4 ins. by ^ in. and 

 wound with 4 layers of No. 16 annuncia- 

 tor wire and screwed to 5 at a point 

 23^ ins. above the base. The strips C 

 and D are of spring brass, 1/64 in. thick 

 by ^^ in. wide, their ends being bent as 

 shown in Fig. II. The strip D, has a 

 piece of soft iron E screwed fast to it 

 at a point opposite the magnet core. 

 The strip C is bent so as to have a 

 tendency to spring up when D is drawn 

 into the magnet. The wiring is clearly 

 shown in Fig. I, 



In operation, the circuit-breaker is 

 placed in series with the battery and 

 the circuit which is to be protected, 

 close to the battery. Should a short- 

 circuit occur on the line, the excess 

 current flowing through the magnet 

 energizes it more strongly than when 

 the normal current flows, drawing D in- 

 ward, thus releasing C, and so breaking 

 the circuit. — E. B. Wilson. 



When the postman raises the mail-box Ud 

 a bell rings in the house 



When a short-circuit occurs, the circuit 



is broken automatically by means of this 



simple device 



How to Make a Rural Mail-Box Alarm 



TO those living in rural or suburban 

 districts, where the mail is deposited 

 in a wooden mail-box by the roadside, the 

 device here described will be of interest. 

 The idea is to have an announcing bell at 

 the house when the mail is placed in 

 the box, and thus make a long wait in 

 the cold unnecessary. An electric bell 

 is put in circuit as depicted, using a dry 

 battery as a source of energ>\ It is 

 advisable to use a roll of insulated bell 

 tape to insulate the wires properly. 

 Two dry cells will be sufficient for any 

 distance up to 200 ft. Cut a thin brass 

 strip and bend at the center. Fasten to 

 the top-extension of the mail-box and 

 connect with the battery. Replace the 

 wooden cover of the mail-box by a 

 brass or metal one. Both the brass 

 strip and metal cover must, of course, 

 be connected with the house by two 

 separate wires. The wires to the house 

 are simply tacked by staples on to 

 small posts. Following is the modus 

 operandi: As soon as the mailman 

 lifts the lid to place the mail in the box, 

 the metal lid comes in connection with 

 the brass strip and closes the circuit, 

 operating the announcing bell at the 

 house. — Wm. Warnecke, Jr. 



Japanese Wireless Telephone 



THE Japanese Navy is equipped 

 with apparatus for radio telephones, 

 with which wireless speech can be 

 transmitted dependably about- ten miles 

 and often three times this distance. 



