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From: edhall@randvax.UUCP
Newsgroups: net.politics,net.misc
Subject: Re: Nuclear Attack Warning Alarm
Message-ID: <1769@randvax.UUCP>
Date: Sat, 21-Apr-84 17:29:08 EDT
Article-I.D.: randvax.1769
Posted: Sat Apr 21 17:29:08 1984
Date-Received: Sun, 29-Apr-84 07:29:46 EDT
References: <391@brl-vgr.ARPA>
Lines: 20

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I seem to remember reading about this in an old (~1960) Popular
Electronics.  The signaling mechanism was *not* changing the power
frequency to 50hz, but was rather the introduction of harmonics of
60hz (3rd or 4th) onto the power grid.  The level of this signal was
only a few volts, and was produced by an arrangement of rectifiers and
resonating circuits. (Changing the basic frequency of electrical power
by 17% is essentially impossible, given the techniques used in power
transmission.)

The PE article showed a test of the device, with people releasing
helium baloons when it sounded off.  It mentioned how tests were
made to insure that the signal didn't damage household appliances
or industrial motors.  I remember wondering about why it made any
difference, and why anyone would even want to know of an attack...
(I was quite young; this was before some people behind us put in
a fallout shelter and before we started practicing `duck and cover'
in school.)

		-Ed