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 modulating one or more c ...

for

computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...

s, released by

AT&T Corporation AT&T Corporation, originally the American Telephone and Telegraph Company, is the subsidiary of AT&T Inc. that provides voice, video, data, and Internet telecommunications and professional services to businesses, consumers, and government agen ...

in 1962. It allowed

digital data Digital data, in information theory and information systems, is information represented as a string of discrete symbols each of which can take on one of only a finite number of values from some alphabet, such as letters or digits. An exampl ...

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 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

Bell 101 The Bell 101 dataset or Bell 101 modem was the first commercial modem for computers, released by AT&T Corporation in 1958 for use by SAGE and in 1959 made commercial shortly after AT&T's Bell Labs announced their 110 baud modulation frequencies. Th ...

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 transmitted through discrete frequency changes of a carrier signal. The technology is used for communication systems such as telemetry, weather ball ...

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 Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 m ...

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency commu ...

, 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 Ca ...

, Canada 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 protocol as opposed to circuit switching or message switching protocols to transmit digital ...

in the HF (shortwave) bands.

Related technology

The

ITU-T The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Co ...

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 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.

Applications

Related technology

In popular culture

See also