Resonant Annunciator to Operate on Alternating Current
The Amateur ■ Electrician And Wireless Operator
HERE is a method of constructing an annunciator to operate on a 110-volt alternating current that is verysimple, yet efficient. There are no sparking contacts in this annunciator; nevertheless 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 frequency 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 watch-case receiver. The cover of the receiver should be unscrewed 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 60watt lamp or something equal in resistance 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 current at all and an ordinary push button may be used; but the wiring and insulation 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 alternations in the CURRENT.--AMP;LT;dc:creator-AMP;GT;JOSEPH BRAFF-AMP;LT;/dc:creator-AMP;GT;.