in reply to Steve

One of my favourite embossers was at Worcester college in the 90's. It was I guess, a very expensive Teal thing, which did two sets of dots at once. I don't remember the combinations, but imagine for example it did Dots 1-4, 2-5, 3-6 and 7-8 if applicable, so it would always do things in three or four chunters at a time.
Each line would usually sound like
Chuh Chuh Chuh> that was one line.
It ran as fast as an HP laser of the time and I've not come across anything quite like it since.
In terms of BPM I'd guess maybe 130 or 140 BPM?
Chuh Chuh Chuh, Chuh Chuh Chuh, Chuh Chuh Chuh...
Sounded like an angry old-school loud London bus ticking over. I'm talking one of the very old types with no doors at the back, which you'd often hear in films from the 60's.