634 



Popular Science Monthly 



An Inexpensive Tester for an 

 Electric Lamp 



THE drawings show how to rig up an 

 inexpensive tester for lamps for use 

 on no, 220 or 440-volt lines. First cut 

 a board as shown in the first sketch, 

 making it about 8 in. in diameter, with a 

 handle long enough for a good grip. 



Lamp sockets on a board cut like a paddle 

 for testing lamps of different voltage 



Then locate four lamp-sockets as shown. 

 If the upper end of the sockets are 

 tapped for a ^ in. pipe, cut nipples long 

 enough to reach through the board. 

 These hold the sockets in place. 



Binding-posts are located at A, B and 

 C. A hole is bored through the handle 

 of the tester, large enough for the lamp 

 cord and connections, as shown. 



The tester may be changed to receive 

 current from any of the three different 

 voltages, by simply attaching the loose 

 end to the different binding-posts, ac- 

 cording to the voltage of the current. 

 In brief: Attaching the end to A makes 

 a circuit for 440 volts, to B, for 220 

 volts, and to C, for no volts. New 

 globes are used in the tester, and the 

 lamp to be tested is placed in the last 

 socket on its circuit. 



An Emergency Electric Plug 

 Made of Broken Lamp 



WHEN the extension plug to the 

 Christmas tree lighting outfit was 

 left loose on the floor, and was kicked 

 into the open grate fire, an emergency 

 plug had to be made in order to hold 



the celebration according to schedule. 

 An old fuse plug was used for this 

 purpose. One wire was soldered to the 

 shell and the other to the brass stud in 

 the center. A disk of fiber with holes 

 for the wires was substituted for the mica. 

 This made a good and serviceable plug, 

 which has been used several times for 

 other purposes. — ^Aaron E. Smith. 



A Mechanical Rectifier as a 

 Wireless Receiver 



IT is well known that the power of the 

 high frequency current set up in a 

 receiving antenna, by the arrival of 

 normally strong waves, is much more 

 than enough to operate a telephone 

 receiver. There is no need of amplifying 

 the effects of this received energy; it is 

 merely necessary to convert it into a 

 form which is suitable for the operation 

 of a telephone or other ordinary indica- 

 tor. Since the radio frequency current 

 itself is too high to cause energetic re- 

 sponse of the regular magnetic tele- 

 phone, the conversion need be merely a 

 reduction in frequency; as an alterna- 

 tive, the energy may be rectified into 

 pulsating direct current. 



The crystal rectifiers which are used 

 in so many stations serve to distort the 

 current of the received waves so that, 

 as it reaches the telephone, it is stronger 

 in one direction than in the other. Thus 

 for each group of waves the diaphragm 

 is attracted or repelled (according to 

 the polarity of the current pulse) a 

 single time. If sustained waves are 

 received it is necessary to break them 



By changing the speed of the interrupter a 

 musical signal of any pitch can be secured 



up into groups, in addition to rectifying, 

 them as just described, if tonal signals 

 are desired. The groups may, for 

 example, be secured through methods 

 involving interrupters, or "beats" pro- 

 duction. 



