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From: Paul Burke
Subject: Re: passive circuit excitation
Date: Mon, 06 Jan 2003 10:41:26 +0000
Organization: Scazon Systems
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Sara Berg wrote:
> hi there group :),
> can anyone tell me whether it is possible to excite a passive
> (dormant)circuit into active operation simply by exposing it to a
> certain radio frequency?
It were called a crystal set when I were a lad. Often called a
transponder these days.
let's say that my telephone's ringing signal
> is XY KHz and i want to place next to it a bulb with a circuit that
> will close only when the phone rings (ie. when the circuit is exposed
> to this XY frequency) thus allowing power to go through it and light
> the bulb.
> does the signal level (amplitude) have any meaning in such a scenario?
The XYkHz is only what you hear. One would hope that the radiated RF
power is 3/4 of zero. Similarly, the actaul ring signal (still, after
all these years, a high amplitude low frequency AC signal) will not give
you any radiated power worth playing with.
You could however detect the rig frequency via a microphone, and use it
to actuate a switch. But you'll have to supply yor own battery.
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