Pretty sure there is no "mute" input on the T3 wiring harness.
There isn't a mute cell phone line. I could think of a few ways to get it working, but would take some hardware and software skills.
- usb gamepad taken apart
- resistor to lower voltage of cell phone mute output of your car kit or use a relay along with the 5vdc from the gamepad
- the idea is that you will be sensing the cell phone mute as a button press
Chuck wrote a cool little peice of software to work with steering wheel controls and a gamepad or joystick. It is called SWC...using the forum information on it you could use this to capture the event and send a "Mute" to SD.
Just thought about it...and you would also need an unmute when the call is over. You could do this with a double throw relay and an additional resistor on the pole for the rest state. You could then have it send key to "un Mute" when the relay goes back to normal state.
If you really want to do this, I can help you along...
Other option, buy Bluetooth phone and StreetDeck BT dongle!
Mitsubishi Eclipse 2006 GT
Infill T3 running StreetDeck
How about using the backup camera signal? assuming you are not already using it for a backup camera and there is a way to capture the input and re-use it for a mute signal.