When I had Viacom cable in the mid 70s, there was no box if you only had the cable channels - it was just channels 2-13, with some UHF channels moved to open channels, so our local Channel 20 was moved to 13, Channel 44 to 12, and so on. But if you had Showtime, Viacom gave you a box with, IIRC, one button on top, which you pushed to watch Showtime, which was then just theatrical movies - no other content whatsoever. And IIRC, it was not 24 hours - but broadcast from late afternoon to a bit after midnight. No censorship whatsoever, though. It was weird at first being able to watch profanity and nudity on TV...this was a half-decade before video-cassettes.