Proximity sensor?

[Andrew Schrock]

On Thu, 30 Sep 1999, Martin Czech wrote:
> :::Sounds very like a device invented in the 20s by a Russian living in America
> :::call Leon Theremin.
> :::He built a device that used a pair of high frequency oscillators and an
> :::antenna, that would generate a sound when someone walked past it.
> :::The idea was it could be mounted in a doorway as an automatic 'doorbell'.
> :::It turned out to have musical applications too.
> :::
> :::You can build a cheap one with cmos logic oscillators, and use a rectifier
> :::to detect the audio output / presence of a body.
> 
> Yes , later on Theremin (french ancestors: Thermin) was kidnapped by the
> KGB and he "disappeared" in some Gulag. He then developped his invention
> in order to control people, ie. motion, position etc.  He also was forced
> to construct espionage devices.

I have to say, Leon Theremin has an insane history, even for the
electronic music field. For more info there's always the movie, although
not having seen it, I can't personally vouch for it. (Maybe somebody else
has and can) 

Andrew

-| Andrew Schrock | aschrock at cs.brandeis.edu |-