Electret Mic without power?

Thanks for the disinformation but my multimeter and two more knowledgeable folks say it's an electret.

 

I guess it goes to show how easy it it to overlook something if we don't know what we are looking for.
I just assumed since you have one of these radios you would have known.

 

sounds nice and intelligible..

 

After working flawlessly for a few weeks, I began to notice occasional feedback.
Does anyone know if it is ok to tie the source lead from the electret together with the transmit wire so they both connect to the shield or common wire when the button is depressed? I have the drain lead from the electret connecting to the audio wire when the button is depressed on another circuit.
Currently using a double pole double throw leaf switch.
Only using shield audio and transmit wires going to the plug.
I though maybe the switch wasn't making a good contact, but I replaced the leaf switch with a DPDT toggle switch and the same issue occurs.
Interestingly enough, the problem does not occur with my Electro-Voice 602 t.
I even tried Bob Heil's fix by connecting microphone Shield to chassis ground and that did not solve the problem.

 

Problem solved. I connected a .1 microfarad capacitor between the shield and the audio wire and it eliminated the squealing problem.