Uh! It makes me remember some obscure and mystic stuff for the IBM 3151 terminal [1]. This terminal has an auxiliary port where you can connect the printer, so it was a (not so) dumb terminal where you can connect other peripherals. There was a government project to attach an individual printer (instead of connecting it to the server) to some terminals but nobody knew the escape codes to control that port. At some point the IBM guys sent a difficult to find IBM 3151 with these details. Probably this manual is now already available on Internet.

[1] http://ps-2.kev009.com/tl/techlib/manuals/adoclib/aixasync/a...