enblethen is correct, while both leads show power in, the black wire is marked -, and the red +. Yes, clock will need to be reset each time switch is off, but seldom look at that clock anyway.
This is an all in one touch screen, or remote controlled am/fm stereo radio, weather radio (with loud emergency alerts), and DVD player, with surround sound speakers.
Only way to shut off touch screen unit, is to disconnect all power to entire trailer.
I want to install switch, just inside cupboard door, right next to unit.
Jerry