An acoustic coupler modem

1978

An acoustic coupler: the handset of an ordinary telephone is pushed into two rubber cups and data is carried as audible tone. This is how a home hobbyist got onto a remote system before dedicated data lines, and it is the device behind almost every 1980s war-dialling story. Slow, noisy and completely unauthenticated. The subject dates from 1978; the photograph itself is later.