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The Bell 103 modem or Bell 103 dataset was the second commercial
PACE is a message terminal that transmits messages over voice circuits
The Bell 103 modem or Bell 103 dataset was the second commercial modem
The Democratic Movement (, ; MoDem ) is a centre to centre-right political party in France, whose main ideological trends are liberalism and Christian democracy, and that is characterised by a strong pro-Europeanist stance. MoDem was establis ...
for computer
A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
s, released by AT&T Corporation
AT&T Corporation, an abbreviation for its former name, the American Telephone and Telegraph Company, was an American telecommunications company that provided voice, video, data, and Internet telecommunications and professional services to busi ...
in 1963. It allowed digital data
Digital data, in information theory and information systems, is information represented as a string of Discrete mathematics, discrete symbols, each of which can take on one of only a finite number of values from some alphabet (formal languages ...
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 oth ...
s at a speed of 300 bits per second
In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time.
The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...
. It followed the introduction of the 110 baud
In telecommunications and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel.
It is the unit for symbol rate or modulat ...
Bell 101 dataset in 1958.
The Bell 103 modem used audio frequency-shift keying
Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is encoded on a carrier signal by periodically shifting the frequency of the carrier between several discrete frequencies. The technology is used for c ...
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, inshortwave radio
Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the High frequency, high frequency band (HF), which extends from 3 to 30& ...
, amateur radio
Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...
, and some commercial applications. 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
Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
, Canada which transmits a Bell 103-compatible digital time code every minute. Bell 103 modulation is also the standard for amateur packet radio
In digital radio, packet radio is the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching Communication protocol, protocol as opposed to circuit switching or message switching protocols ...
in the HF (shortwave) bands.
Related technology
The ITU-T 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 bandInformation Society
An information society is a society or subculture where the usage, Content creation, creation, information distribution, distribution, manipulation and information integration, integration of information is a significant activity. Its main drive ...
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.
See also
* Bell 202 modem * List of device bandwidthsExternal links
PACE is a message terminal that transmits messages over voice circuits
References
{{DEFAULTSORT:Bell 103 Modem Modems AT&T Telecommunications-related introductions in 1962 Bell System modem standards