A telecommunication control unit (TCU), line control unit, or terminal control unit (although terminal control unit may also refer to a terminal ''cluster controller'') is a
Front-end processor
A front end processor (FEP), or a communications processor, is a small-sized computer which interfaces to the Host (network), host computer a number of computer network, networks, such as Systems Network Architecture, SNA, or a number of Periphe ...
for
mainframes
A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...
and some
minicomputer
A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ...
s which supports attachment of one or more
telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than tha ...
lines.
TCUs free processors from handling the data coming in and out of
RS-232
In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' ('' data terminal equipment'') suc ...
ports. The TCU can support multiple terminals, sometimes hundreds. Many of these TCUs can support RS-232 when it is required, although there are other
serial interfaces as well.
The advent of ubiquitous TCP/IP has reduced the need for telecommunications control units.
See also
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Terminal access controller
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IBM 270x 270x is a generic name for a family of IBM non-programmable communications controllers used with System/360
The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered betwee ...
*
IBM 3705 Communications Controller
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IBM 3720
The IBM 3720 was a communications controller (front-end processor) made by IBM, suitable for use with IBM System/390. The 3720, introduced in 1986, was capable of supporting up to 60 communications lines, and was a smaller version of the 3725. Of ...
*
IBM 3745
The IBM 3745 is the latest and last of a 37xx family of communications controllers for the IBM mainframe environment. As of mid-2009 there were an estimated 7,000+ of the larger 3745 models still in active production status, down from 20,000 or m ...
References
Mainframe computers
Networking hardware
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