Bell 103

[1][2] It allowed digital data to be transmitted over regular unconditioned telephone lines at a speed of 300 bits per second.

For many years, higher-speed modems retained the ability to emulate the Bell 103, allowing a fallback method for data to be communicated at low speed if channel conditions deteriorated.

Its low signalling speed and use of audio frequencies makes it suitable for noisy or unreliable narrowband links.

One example is the CHU shortwave station in Ontario, Canada which transmits a Bell 103-compatible digital time code every minute.

The American synth-pop band Information Society featured a track entitled "300bps N, 8, 1 (Terminal Mode or Ascii Download)" on their album Peace and Love, Inc. that could be decoded to a text message by holding a phone handset connected to a Bell 103 modem up to the speaker playing the track.