HOWLING_BOX

Published:2009/7/7 20:40:00 Author:May | From:SeekIC

Tone oscillator driving loudspeaker is sealed into wood or plastic box, with reed switch mounted on one face of box and pushbutton of other switch projecting out through hole in box. Place DO NOT TOUCH label on button. When button is pushed despite yvaming, SCR latches and applies power to AF oscillator. Only way to turn off howling is to hold large permanent magnet against location of reed switch, to oppose field of magnet glued on switch and make reed contacts open. If mercury swhch is used in box in place of pushbut-ton, alarm goes off when box is picked up.-P.Walton, Now What Have I Done?, 73 Magazine, May 1975, p 81.



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