I'm watching Mad Men, S4, Ep7 and they're talking about going to a theater where they can watch the fight on "closed circuit". I'm wondering how. As far as I know, projectors needed film before the digital age. How does a 60s era live projector work? (some sort of overly bright CRT and lenses?)
It's possible the writers of Mad Men took some liberties with technologies to get the story they wanted, but I hope that's not the case as the rest of the show certainly lines up with history very well.