Is the connector for the mic stereo or mono?

I'm about to build and redesign a mic (which was coming out of a handsfree-set) to fit into the car.
There's something like a filter or mini-amplifier or something like that connected to the mic. 3 wires are coming out of the mic and 2 wires are coming out of this mini-amp (or whatever this is).

I don't really know what for there are 3 connections on the mic (I think it is not a stereo mic - there would be no use for it)

TeeMcBee