Hi pebe,
I'm not quite sure which post was addressed in your comment.
You are absolutelly correct about crystal and carbon microphones.
One thing they have in common, both are pretty much obsolete
and hard to find nowdays.
It is not difficult to condition signal of one microphone type to
simulate other type (well, within limits of course. nobody should
expect studio quality recording done with carbon mic).
I guessed that some newbe was having hard time to get his first
microphone work. Typical first time project using microphone is a
small transmitter and many old circuits relied on chrystal microphones.
So I tried to help with something robust enough to work with just
about any microphone. As a matter of fact, carbon mic can be
used as well in the provided schematic. To do so, R1 can be removed
(it doesn't have to). Replace Mic on schematic with a jumper and
insert carbon mic between T1 emitter and negative pole of the battery.
That's all it takes. Chrystal mic was often used for simplicity of the circuit because it provides pretty high signal and it has high impedance. To
connect it to my circuit, everything on the left side of C3 can be removed including C3. Chrystal mic would be connected directly to base of T2.