On Thu, 26 Dec 2002, Rich wrote:

*>It seems that the author of the article introduced an AC signal (50 Hz HUM)
*>into an analog input or sensitive counter input.  I did not read the
*>article, but that is a trick that I have used many times to see if a signal
*>is amplified or at least detected.  We are a pretty good antenna and we pick
*>up the AC HUM and transfer it to an input quite easily.  I would definitely
*>be suspicious of the circuit.

Unless of course you are touching ground at the time, your feet are wet,
or you are in a metal-filled room or cubicle, all grounded properly. Or
far away from any mains circuits. Did I leave anything out ?

Otoh you can check if you are 'humming' right by touching the audio (!)
input of an available audio amplifier, radio, etc.

Peter

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