This was a problem I solved and thought it would be nice to share the solution. This may only apply if your trailer came with an included TV and builtin Touch Audio DVD/Radio/ mini-deck.
THE ISSUE: The Touch Audio mini-Surround Sound built-in deck only has one INPUT using a pair of analog -type R/L jacks for an external sound source to input. Sound Output from the deck is not an issue, just input is. The DVD sound goes to the as does, FM radio etc. When you are watching a DVD, the video goes to the TV but the audio goes to the ceiling. But when you play the TV say for a local channel, the TV's sound only comes from the built-in TV speakers, not the ceiling speakers. This is fine if the A/C isn't running full blast. If it is, even having the TV turned up full volume can make it difficult to hear. If you look at the back of the TV, the is limited to either a headphone jack or the digital port labeled 'Coaxial' (don't confuse this port with the antenna coax, Coaxial looks like a singel RCA-type jack).
TECHNICAL NOTE: You will need to be able to get to the jacks at the back of the Touch Audio deck. For my trailer, this was a simple when I removed to screws to get to the access panel. For others, you may have to slide the deck out to the front (see the Touch Audio manual).
SOLUTION 1: You can get a simple converter cable at for Headphone mini-plug to Analog RCA R/L and use that to connect the TV to the audio INPUT jacks at the back of the Touch Audio deck. Downside for this is that the TV's internal speakers are disabled and you will only get sound from the ceiling and not from TV itself. Depending on where your flat panel is mounted, this may not be comfortable to listen that way.
SOLUTION2: Purchase a DAC converter on Amazon for $16. This litte unit is about the size of a small zippo lighter. It comes with a small power adapter that will plug in where your TV is plugged in. The unit has a 'Coaxial' port on one side and 2 RCA R and L on the other that you will use to connect the DAC's R and L outputs to the Touch Audio's R and L inputs (labeled TV audio input in the manual). Do it this way and you get sound from both the TV speakers and the ceiling speakers. The only downside is if you want to watch TV inside while piping music to the outside. If that's your desire, then TV sound will be TV only, while you will select something else besides mode AUX on the mini-deck to feed the ceiling and outside. Make sure you go thru the setup on your TV and set the Digital Output to PCM. One caveat here: Sometimes I have to reset the DAC because the Touch Audio failed to recognize the signal.
LAST COMMENTS: When I picked up my trailer, the dealer had connected the TV's Analog RCA inputs to the mini-decks inputs. Connecting Input to Input didn't cause any problems, it just didn't provide any funtionality.