I personally use a portable intercom with an audio out jack.
John T

John,
I have a portable David Clark intercom with the audio out jack,
but when I picked up a cable at Radio Shack and plugged it into my
Sony camera (mic input) it didn't pickup any sound.
The camera does however state (plug in power) just below the mic
input but I'm not quite sure what that means.
Any suggestions?

David (KORL)