Look for a plate similar to this one. Many rigs have it in the bedroom, but that's not cast in stone. The newer ones have a round push button instead of the slide switch, but they work exactly the same. On for TV with over the air antenna (OTA), and off for cable or satellite use. The led lights up when the amp is on. Some of these plates may not have the 12vdc outlet, but they all should have the F connector for the line to the TV.
Also there are many previous threads and posts on this exact topic. It's worth searching them out and reading through them.
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'11 Cougar 326MKS loaded with mods
'12 Ford F250 SuperCab 6.7 PowerStroke Diesel
Amateur Radio: KD2IAT (146.520)
GMRS: WQPG808 (462.675 TPL 141.3)