[s1mon]

I'm old enough and lucky enough to have had my first computing experiences (1978-80) be on a teletype in our elementary school which was connected to a minicomputer that the town owned. The connection was an acoustically coupled modem/analog phone line that ran at 300 baud. The exciting thing was to write very basic BASIC programs and see results on the printout. There was no CRT, everything was via the literal teletype - a keyboard and a clunky printer.

[joak]

You could use this audio at 300 baud by recording it on a standard audio cassette. Then play the audio back as input to the modem to retrieve the data

[anthk]

Minimodem does this.