Ok, You have a switch with a red light to let you know the antenna amplifier is turned on. You can plug the tv into the 12volt outlet, only if you have a 12vout/110volt tv. The tv needs a 110volt outlet! If there is a place for the tv to sit there most be a outlet for it. I wouldn't think that they would not have put in a 110 outlet. Only thing it could have happened is if the previous owner did the install himself. He may have had a tv/vcp that worked on 12 volt! Without more info, It would be hard to make another assumption! Maybe someone else might be able to shed some light on the subject!
Welcome to the forum, I;m sure someone has run into this before. Ours didn't have the amplified antenna. but did have a 110 outlet. They put there own shelf in and outlet and wired across the roof to antenna. Good luck and we willl look forward to your adventures!