Some motor-homes from that time-frame may have come with an inverter that would only power the outlet the overhead television would use. It would have most likely been an option.
There may be an on/off switch in one of the overhead compartments, or maybe the unit was "on" unless the house-battery "disconnect" was used to take the batteries off line.
You might see if the television will turn on when not plugged into shore-power and batteries connected to the circuit. I would be very surprised if any other 120v,ac, outlets were powered by the inverter since it would discharge standard batteries supplied by manufacturer too quickly if used that way.
Mark & Jan "Old age & treachery win over youth & enthusiasm"
2003 Fleetwood Jamboree 29