A terminal adapter or TA is a device that connects a terminal device – a computer, a mobile communications device, or other – to a communications network.

ISDN

ISDN Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. ...

terminology, the ''terminal adapter'' connects a ''terminal'' (computer) to the ISDN network. The TA therefore fulfills a similar function to the ones a

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 ...

has on the POTS network, and is therefore sometimes called an ISDN modem. The latter term, however, is partially misleading as there is no

modulation Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information. The process encodes information in form of the modulation or message ...

demodulation Demodulation is the process of extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content fro ...

performed. There are devices on the market that combine the functions of an ISDN TA with those of a classical modem (with an ISDN line interface). These combined TA/modems permit connections from both ISDN and analog-line/modem counterparts. In addition, a TA may contain an interface and

codec A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...

for one or more analog telephone lines (aka ''a/b line''), allowing an existing POTS installation to be upgraded to ISDN without changing phones. Terminal adapters typically connect to a

basic rate interface Basic Rate Interface (BRI, 2B+D, 2B1D) or Basic Rate Access is an Integrated Services Digital Network (ISDN) configuration intended primarily for use in subscriber lines similar to those that have long been used for Plain old telephone service, ...

( S0, sometimes also U0). On the ''terminal'' side, the most popular interfaces are

RS-232 In telecommunications, RS-232 or Recommended Standard 232 is a standard introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such as a compu ...

serial and

USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...

; others like V.35 or

RS-449 The RS-449 specification, also known as EIA-449 or TIA-449, defines the functional and mechanical characteristics of the interface between data terminal equipment, typically a computer, and data communications equipment, typically a modem or te ...

are only of historical interest. Devices connecting ISDN to a network (e.g.

Ethernet Ethernet ( ) is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...

) commonly include

routing Routing is the process of selecting a path for traffic in a Network theory, network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched ...

functionality; while they technically include a TA function, they are referred to as (ISDN) routers.

Mobile networks

mobile network A cellular network or mobile network is a telecommunications network where the link to and from end nodes is wireless and the network is distributed over land areas called ''cells'', each served by at least one fixed-location transceiver (suc ...

s, the ''terminal adapter'' is used by the

terminal equipment In telecommunications, the term terminal equipment has the following meanings: * Communications equipment at either end of a communications link, used to permit the stations involved to accomplish the mission for which the link was established. * ...

to access the mobile termination, using AT commands (see

Hayes command set The Hayes command set (also known as the AT command set) is a specific command language originally developed by Dale Heatherington and Dennis Hayes for the Hayes Smartmodem in 1981. The command set consists of a series of short text string ...

). In 2G (such as

GSM The Global System for Mobile Communications (GSM) is a family of standards to describe the protocols for second-generation (2G) digital cellular networks, as used by mobile devices such as mobile phones and Mobile broadband modem, mobile broadba ...

CDMA Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communicatio ...

), the terminal adapter is a theoretically optional while in 3G (such as

W-CDMA The Universal Mobile Telecommunications System (UMTS) is a 3G mobile cellular system for networks based on the GSM standard. UMTS uses wideband code-division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency ...

), the terminal adapter is mandatory and is part of the mobile termination.

Automation industry

In the

automation Automation describes a wide range of technologies that reduce human intervention in processes, mainly by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machine ...

industry, a ''terminal adapter'' is a ''passive'' device that converts a connector like the

8P8C A modular connector is a type of electrical connector for cords and cables of electronic devices and appliances, such as in computer networking, telecommunication equipment, and audio headsets. Modular connectors were originally developed for ...

(RJ-45)

modular connector A modular connector is a type of electrical connector for cords and cables of electronic devices and appliances, such as in computer networking, telecommunication equipment, and audio headsets. Modular connectors were originally developed fo ...

or 9 pin D-Sub into a terminal block to facilitate wiring. It is often used when

daisy chain Daisy chain may refer to: * Daisy chain, a garland created from daisy flowers * Daisy chain (climbing), a type of strap * Daisy chain (electrical engineering) In electrical and electronic engineering, a daisy chain is a wiring scheme in whi ...

wiring is necessary on a multi-node serial communication network like

RS-485 RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. Electrical signaling is balanced, and Telecomm ...

RS-422 RS-422, also known as TIA/EIA-422, is a technical standard originated by the Electronic Industries Alliance, first issued in 1975, that specifies the electrical characteristics of a digital signaling circuit. It was meant to be the foundation ...

ISDN

Mobile networks

Automation industry

References

See also