Thinking ahead to making a mobile headset microphone I decided to investigate the microphone connections for the MD9600.
It appears that the microphone circuitry is almost a direct copy of the Yaesu MH-48, the service manual for which can be found on the internet.
The 8 pin RJ45 connections are as follows...
1 Keypad Column
2 Keypad Row
7 Not connected
8 Not connected
PTT connects to Ground Via a diode and a 100 Ohm resistor.
Keypad row and column pins have different resistances switched to ground depending on which key is pressed. Presumably the CPU in the radio reads this with an ADC as 2 variable voltages. The keypad is arranged as 5 rows of 4 columns.
This opens up the potential of making an LCD touchscreen and headset to replace the microphone which could then be placed in a convenient location in a vehicle. It may even be possible to program sequences of button presses to make complicated functions a one press action.
I can feel a winter project coming on.......
73 Colin G4EML