HA, HA!! I'm first...I won!!
does this button have to be on if you're using the tv in the living room? been watching lots of dvd's. (we've only boondocked with the trailer since we've had it, probably seem like being at the Ritz if we were plugged in).
Well its been answered what it is, and when you need it. But when your unit is in storage, make sure the light is off or it will drain your battery.
Dave