OK I have checked on the stuff:

If the 'Mute' is set to '12V', what I have described above happens:
If I turn the lights on, the display goes dim (can be adjusted by the dimmer settings as suggested above), the phone icon appears and it's on mute. When I turn the light back off, it stays in mute and there is no was to get it back out unless I reset the player.

When 'Mute' is set either to off or 0V, the dim just works normal on 'lights-on', but of course phone mute doesn't work. Mute works under no condition therefor. Sorry can't send mail to empeg my mailserver just crashed. Tks, J.