Re: what fun it was writing configuration scripts in the Hayes ‘language
My favorite off-label modem use: as a primitive speed-dialer.
1987. We badly, badly wanted tickets to the upcoming Pink Floyd concert. In those pre-Internet days [1], the way to get them was by phone. Problem: world+dog wanted the same thing we did, so getting through was a matter of blind luck. So we all sat at our phones, dialing and dialing and dialing.
Unlike my friends, I had a computer -- my first, an Amiga 1000 -- and so, an optimization was available. I got into the terminal program and used the modem to dial the ticket company's voice line [2], prepared to pick up the phone and then type <space> to make the modem hang up, should I actually get through. I got a busy signal of course, but then it was a simple matter of "a/" (which meant "redial the last number"), wait for busy, <space>, repeat. For at least a couple of hours.
That shortened the retry interval a lot, vs manual dialing -- and so, I figured, greatly improved my chances. Even so, it wasn't me who finally got through, but one of the others who, all that time, had been redialing the hard way.
Not only didn't I ever connect, but in all those hundreds(?) of attempts, I only once or twice got a normal busy signal. The rest of the time it was fast busy, which meant upstream network congestion -- that's how swamped the system was.
[1] Yes, I know. I'd even heard tales of it. But as far as the general public were concerned, including my long-out-of-university self, it might as well not have existed.
[2] I can't recall whether that was still BASS (Best Available Seating Service) or whether they were already Ticketmaster by that point.