You're both right. The initial prototype with essentially 2 separate side-by-side TVs was from 1945. But the more interesting (IMO) approach was the 1954 "Duosc

You're both right. The initial prototype with essentially 2 separate side-by-side TVs was from 1945. But the more interesting (IMO) approach was the 1954 "Duoscopic" version that showed 2 programs on the same screen, and each viewer looked through a polarized panel (and had their own headphones) to view their particular program: https://www.earlytelevision.org/pdf/dumont_duoscopic_brochure.pdf https://www.earlytelevision.org/pdf/dumont_duoscopic_brochur...