I wrote about such a design in Kitplanes within the last three years or so.
If you are really interested, I can dig down into the archives and see what
month and year.

Basically, you bias the mic on and use the volt or so of audio through a
capacitor to run the earphones. If you can hear yourself talk, the headset
is working. No amplifier or intercom required.

Jim



"M." wrote in message
...
Hi all

Does anyone have a copy of a circuit diagram to construct a headset
tester?
I'd like to construct one to test the headsets students are returning
claiming them to be faulty, which after I've headed out to the flight line
and plugged in, surprise surprise, there is no apparent fault.

Any help

Cheers Mike