Hello! Recently, my friend gave me a ps1. He lives in a hotel, and found a stack of them in his basement. However, these don't seem to be normal - they have a red rca cable coming out the back (just underneath the AV multi-out)! There is also a sticker that says "prodac" on it, along with some serial numbers. My friend says that the systems were used for some sort of "on demand" gaming service in the hotel rooms back in the day, and so our guess is that this cable is for older TV's or something, and the systems were modded to support them. Anyway, I would quite like to know what this is, even if you can only offer a guess. I have tried plugging it into a composite port and an audio port, but nothing happened. I'm willing to open it up if you think it's necessary. It might be worth mentioning that the AV out still works on the system, as does seemingly everything else. Thank you in advance!