"jimdandy45" wrote ...
I have a multiple input TOA A-903A mixer/ampifier. We use Cartioid
Dynamic 600 ohm mics. Is it possible to replace one with an over the
ear cell phone headset with a "boom" mic?

Yes. But 99.9% of those cell phone headsets use electret
condenser mic capsules which require power to operate.
There are some circuits on the www.epanorama.net web
which describe how to power an electret capsule. There
are no commercially available devices to do this as there
is not much call for it.

Any idea if this would be a balanced or unbalanced connection?

All those electret capsules are unbalanced. You can be
sure that your's is also.

Purpose would be to have the mic right by my mouth, and not have to
hold the heavy mic or have the heavy mic in a holder and have to lean
over to it. Specifically I want to use it this way as the caller for
Bingo games.

the mic connection, I believe, is:
,-------------------earth
O O ------------common
O -------------hot

This sounds typical for a balanced, dynamic microphone.