ELECTRET without DC?

Using the ELECTRET microphone without a DC supply !

Well not really, but with this "trick" you can replace an existing microphone insert in a 'fist' microphone housing etc, without the need to provide a separate DC supply to power the electret element.

Referring to the diagram shown : it can be seen that the PTT (push-to-talk) line is now grounded through two series silicon diodes (much like a Zener diode) which will then provide a source of DC potential to energise the electret element. In most cases the PTT line although now not pulled down to ground but 'clamped' to 1.4 volts will still operate the radio its connected to. Its certainly worth a try.