454 



Popular Science Monthly 



OlAECTIOtt Of REVOLUTION — 



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THIS END OF CONTACT- 

 WIRE FASTENS TO 

 LEAD FROM BELL 



Making Your Window Tappers 

 Tap Intermittently 



AS a contrivance for attracting atten- 

 l\ tion to window displays, the electric 

 window tapper has lost some of its former 

 value, simply because 

 people have become so 

 used to its buzzing sound 

 on the glass that they will 

 not stop to look. The de- 

 vice can be restored to its 

 former usefulness, how- 

 ever, by a very simple ex- 

 pedient. Secure an or- 

 dinary clock and around 

 a spoke on one of its gear- 

 wheels twist a piece of 

 wire in such a way that 

 the loose ends project out- 

 ward from the face of the 

 wheel and form a pin A. 

 This pin can be made to engage two or 

 more contact wires at every revolution of 

 the wheel. Thus an automatic circuit 

 breaker is formed. This circuit-breaker, 

 when introduced into the wiring of the 

 window tapper in the manner shown in the 

 illustration, will cause the tapper to buzz 

 at intermittent, and to an observer going 

 past the window, unexpected intervals. 



Two or more tappers, as the illustration 

 shows, can be attached to the same circuit 

 breaker, simply by mounting the corre- 

 sponding number of contact wires in such 

 position that the pin on the gearwheel can 

 touch them in its revolving. The tappers, 

 when placed in unexpected parts of the 

 window, rarely fail to make a marked im- 

 pression on a passer-by. As can be ob- 

 served by studying the wiring, the pin on 

 the gearwheel in revolving connects with 

 first one of the contact wires, then the 

 other. This causes the two tappers to buzz 

 alternately, and for a short time only, in- 

 stead of steadily, as is ordinarily the case. 

 To a passer-by, the resulting sounds are as 

 if a Hallowe'en "tick-tack" had suddenly 

 gone off, and he stops to see what caused 

 the commotion. By that time, however, 

 the sound has ceased. But just as he is 

 about to move on, the other tapper comes 

 into action in some other quarter of the 

 window with its own "tick-tack" — this 

 due to the fact that the pin on the clock 

 wheel has in the interval proceeded far 

 enough to engage the other contact wire. 

 Again the passer-by halts. In such manner 

 the contrivance works all day long, focus- 



Wiring diagram to an old clock for 

 making an intermittent current 



sing the attention of the passing crowds. 

 In the drawing below the two contact 

 wires B are shown mounted on the corner 

 screws of the clock frame. To do this it is 

 first necessary to envelop the heads of the 

 screws and a small part of their length with 

 short bits of rubber tub- 

 ing. The contact wires 

 are twisted tight to this 

 rubber tubing, the latter 

 thus insulating them from 

 the screws. If the con- 

 tact wires were not insu- 

 lated in this way they 

 would make direct con- 

 nection through the clock 

 frame to the wire at- 

 tached to its bottom post 

 and thus keep the tappers 

 buzzing steadily — which 

 is not desired. The only 

 precaution necessary in 

 erecting this apparatus is to see that the 

 contact wires are insulated from the frame 

 of the clock. — Lloyd E. Darling. 



A Vibrating Ticker Interrupter 

 Made Out of a Buzzer 



A BUZZER, modified as shown in the 

 illustration, may be used as a "ticker" 

 or "chopper" for receiving undamped wire- 

 less waves, or as an independent interrupter 



TO K CONNECTED IN SERIES WITH PRIMARY OF COO. 

 OR IN SECONDARY CIRCUIT OF RECENING SET 



| SILVER CONTACTS 



Two vibrators or buzzers may be combined 

 to give a multiplied vibration frequency 



for small spark-coils. The instrument can 

 be constructed from one or two ordinary 

 buzzers (depending on the frequency re- 

 quired). When it is to be used as an inter- 

 rupter it should be fitted with large contacts 

 and a suitable condenser. — Werner Staaf. 



