The first modem I saw was a telephone plugged into an acoustic coupler, run by a 64k BBC Micro computer in BASIC or assembler. I also drove traffic lights from it, and added x2 2 8-bit bit bytes together using a carry in assembler. *One point I didn't think anyone thought of is the 'Doomsday Project' they had in 1986 where by schools put text and pictures about their present communities on BBC Disk BEFORE the internet. But a quite search found someone HAS transferred the data from the unreliable 5.25" Magnetic Disks:
Maplin Project Book Seven, 1983 – ZX81 300 Baud Modem
Maplin Project Book Eight, 1983 – Dragon 300 Baud Modem
baud - definition:
baud was the prevalent measure for data transmission speed until replaced by a more accurate term, bps (bits per second). One baud is one electronic state change per second. Since a single state change can involve more than a single bit of data, the bps unit of measurement has replaced it as a better expression of data transmission speed.
The measure was named after a French engineer, Jean-Maurice-Emile Baudot. It was first used to measure the speed of telegraph transmissions.