The Bell 103 modem or Bell 103 dataset was the second commercial

modem A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...

for computers, released by

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in 1962. It allowed digital data to be transmitted over regular unconditioned

telephone line A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or ot ...

s at a speed of 300 bits per second. It followed the introduction of the 110 baud Bell 101 dataset in 1958. The Bell 103 modem used audio frequency-shift keying to encode data. Different pairs of audio frequencies were used by each station: * The originating station used a mark tone of 1,270 Hz and a space tone of 1,070 Hz. * The answering station used a mark tone of 2,225 Hz and a space tone of 2,025 Hz. Although original Bell 103 modems are no longer in common use, this encoding scheme is referred to generically as "Bell 103 modulation", and any device employing it as "Bell 103-compatible" or "a Bell 103 modem". 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.

Applications

Bell 103 modulation is still in use today, in shortwave radio, amateur radio, and some commercial applications. Its low signalling speed and use of audio frequencies makes it suitable for noisy or unreliable narrowband links. For example, the CHU shortwave station in

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...

, Canada transmits a Bell 103-compatible digital time code every minute. Bell 103 modulation is also the standard for amateur packet radio in the HF (shortwave) bands.

Related technology

The

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V.21 communications standard defines a very similar modulation scheme. Commercial 300 baud modems typically support both formats.

In popular culture

The American synth-pop band

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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.

Applications

Related technology

In popular culture

See also