Page:Popular Science Monthly Volume 91.djvu/470

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��Popular Science Monthly

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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.

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