Allodoxaphobia writes:

On Sun, 29 Mar 2009 01:44:49 GMT, William R. Walsh wrote:
Hello all...

I was cleaning up some stuff in the basement when I found a cardboard box
with a Newsweek address on it. Opening it revealed a small white-cased
device with an on-off pushbutton and a speaker. It uses 4 double-A
batteries. There are no other controls or indicators on it anywhere.

I first thought that it had to be some kind of a fixed-frequency radio,
probably something that was tuned to one AM station for promotional purposes
or maybe even a weather radio. But it doesn't seem to receive
anything--assuming it even works. With batteries in place, it would hum
(much like ground loop hum) and the sound would get louder near electrical
wiring. I never heard any sort of station or static.

Taking it apart revealed a very simple circuit board with a coil, power
switch, a few small transistors, some resistors and a few caps. It's really
very simple--too simple to be any kind of radio I'd know about. The one IC
on it is an STMicroelectronics TBA820M audio amplifier, with a date code of
early 1988. Running it while taken apart revealed a few things--let the
circuit board get near the battery compartment or wires, and the speaker
would go into feedback. The coil on the board was sensitive to touch or
metal tools--and produced a "tapping" sound in the speaker when touched. It
was not sensitve to other random objects on my workbench. I also found that
I could feed audio into one of the connections on the coil and hear it
clearly through the speaker.

A picture of the circuit board is he
http://greyghost.mooo.com/newsweek-radio.jpg (541x255, 47KB)

Probablty a Stud Finder -- locates the nails in the drywall hammered
into the stud.

I have one of these things. The circuit board is identical to the
one in the pic.

At first, I did think it was some sort of telephone amplifier.

But now I'm inclined toward the stud or wiring finder type of application.

This is a small embossed arrow next to the on/off switch that lines
up with the coil.

Mine buzzes to some extent all the time, but is sensitive to ferrous
and/or magnetized objects near the coil. It squeels in various ways
depending on size, orientation, magnet strength, etc.

--
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