Page:Popular Science Monthly Volume 92.djvu/163

 �Q AmatQur • Electrician

��I'^nd Wii'Gless Operator

��Resonant Annunciator to Operate on Alternating Current

HERE is a method of constructing an annunciator to operate on a 110-volt alternating current that is very- simple, yet efficient. There are no spark- ing contacts in this annunciator; never- theless it admits of a wide range of tone adjustment and gives forth a powerful buzzing note that is exceptional because of its unusual resonance, its extremely low pitch and enormous volume. The pitch may be regulated to a higher fre- quency and smaller volume, which may be necessary when the far-reaching, low, powerful note is not desired, as may be the case when there is someone ill in the house or where for any other reason it is necessary to minimize the noise of the instrument.

The annunciator consists of nothing more than a 75-ohm w^atch-case receiver. The cover of the receiver should be un- screwed nearly all the way when the low pitch is desired. By screwing the cover on tighter, the pitch is raised. To secure best results, the receiver should be mounted at an angle slightly off vertical, or in other words, with the face of the receiver-cover tilted downwards. A 60- watt lamp or something equal in resist- ance to it should be placed in series with the annunciator in order to lower the amperage of the current passing through it and thus serve to protect its windings.

The device will consume hardly any cur- rent at all and an ordinary push button may be used; but the wiring and insula- tion should be much heavier than for ordinary battery annunciators. It is, of course, readily understood that the buzz produced is the effect of the rapid alterna- tions in the current. — Joseph Braff.

��Making a Night Light of Battery Cell and Miniature Lamp

A SIMPLE, yet efficient night light can easily be constructed by follow- ing the instructions outlined in the ac- companying illustration. If the necessary materials are not at hand, they may be purchased at any electrical store. The base and the upright are made of wood, and fastened together with two flat- headed screws. A felt pad, cut to shape and pasted on the bottom, will prevent the polished surfaces from being scratched.

��CLMi/IP

��-SMALL LAMP

���PUSH BUTTON^

A dry cell placed on a base with upright to hold watch and lamp for a night light

The battery is held in place by a wire bound around it and attached to a staple on either side. The lamp, preferably a 2 3^- volt tungsten, is connected in series with the button and battery. For running the wires from the lamp to the back of the board, insulated staples should be used.

A twisted No. 20 lamp cord is used. Its length depends upon the distance between the bed and the article upon which the night light is to be placed. The sketch shown above makes the construction clear. — H. Neuhaus.

�� �