Hotel TVs do tricks to support the ondemand systems. oncommand was one and there was another. When someone hits menu it would secretly jump the tv to an unused channel and the hotel headend would generate menus for that user bbrowsing. Buy a movie and you get on a dedicated private channel where you can see it. We could get the tvs into add/remove channel mode and you could just go up thru the channels and see people browsing menus, watching movies and sometimes naked people. Good av hardware supports rs232 for integreation with control systems like AMX and Crestron. I moved off AMX to this linux python pile called HomeAssistant and it's on my to-dos to add a serial to network bridge and make home assistant talk to my home stereo preamp which has rs232. Home assistant is wild, it's crazy but also crazy powerful. - Ethan