See also:

MUTE button (if equipped)
Press this button if you wish to immediately cut the volume to zero. The audio display will show “MUTE”. If you press the button again, the original sound volume will return and “MUTE” turns off. ...

Acc
In this position the electrical accessories (radio, accessory power outlet, etc.) can be used. ...

Precautions against vehicle modification
WARNING To avoid accidental activation of the system or rendering the system inoperative, which may result in serious injury, no modifications should be made to any components or wiring of the SR ...