This page contains information related to the microphone on the FT100 and a few other Yaesu radios

Mic-jack Yaesu FT-100 / 90 / 8100.

Pin 1: SW 2 multi-function switching for P, P1, P2
Pin 2: N.C. (9600bps packet data output FT-90)
Pin 3: + 9 V
Pin 4: GND
Pin 5: Microphone Input
Pin 6: SW 1 PTT, UP,  DOWN, Acc

The above information courtesy of  Bjorn, SM5SWI


The diagram above is courtesy of John, F5FML.

The number keys and A, B, C, and D keys on the MH36 microphones (standard on the FT100 U.S. models) generate DTMF tones on the microphone input.