MC-53DM DTMF MICROPHONE.

  

                                  PIN 1 UP.
                                  PIN 2 +8 VOLTS.
                                  PIN 3 CHASSIS GROUND.
                                  PIN 4 PTT.
                                  PIN 5 MIC GROUND.
                                  PIN 6 MIC.
                                  PIN 7 RX AUDIO.
                                  PIN 8 DOWN.