The Bell 212A modulation scheme defined a standard method of transmitting
full-duplex
A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...
asynchronous serial data at 1.2 kbit/s over analogue transmission lines. The equivalent, but incompatible
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 Comm ...
standard is
V.22.
Device
The Bell 212 Dataset is a 1979-vintage
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 ...
used for communicating over telephone lines at 300 or 1200 bits per second.
The 212A standard provides for the ability of a modem to auto-answer a ringing phone.
[
]
Usage
The Bell 212A scheme was the most common standard used for 1200 bps transmission on US data networks such as CompuServe during the period that dial-up Internet access was the norm (1980s and 1990s).[Frank J. Derfler Jr.]
"Selecting the right modem"
''PC Magazine'', pp. 224-233, January 1983.[Frank J. Derfler]
"The Universal Data Systems' 212 LP modem"
''InfoWorld'', pp. 52-53, 9 August 1982.
See also
* List of device bandwidths
References
Data transmission
{{Telecomm-stub
Telecommunications-related introductions in 1979