HTX100 Microphone
Information from the Realistic Service Manual By Rogerbird

HTX100 Microphone Plug Wiring

Pin 1 = Audio (+)
Pin 2 = Transmit (TX)
Pin 3 = Channel Down Button
Pin 4 = Channel Up Button
Pin 5 = No connection
Pin 6 = No connection
Pin 7 = Sheild/Audio (-)
Pin 8 = No connection