[Beermotor]

I'm going from 30+ year old memories as an intern, but from what I remember:

Usually the RS232 was just on the terminal side. Somewhere along the path it got converted to twisted pair.

All the twisted pair serial lines congregated in the server room at a punch-down box. Eighteen year old me wasn't allowed to mess with anything past that point, but from what I can remember those lines were concentrated by a multiplexer (mux) and sent on to the minicomputer.

[AnimalMuppet]

I think you're right. I remember seeing a lot of ads for muxes in the Datamation magazines I read as a kid.

I can't give any details about them, because well, I was a kid, and the details of what they were talking about were beyond me...