telematics—User-oriented ISDN information transfer services (e.g., teletex, videotex, facsimile).
Teleservices—A telecommunications service that provides the complete capability for communication between subscribers according to protocols agreed to by RPOAs. A set of ISDN features using communications links, including E-Mail and fax services.
Teletext—A telecommunications service that provides a one-way information retrieval service that uses unused portions of a TV channel bandwidth. A fixed number of text pages are repetitively broadcast for decoding by a decoder at the TV set that can select and display pages. See also ISDN.
terminal—The screen and keyboard device used in a mainframe environment for interactive data entry. Terminals have no box, which is to say they have no file storage or processing capabilities.
terminal adapter (TA)—An ISDN DTE device for connecting a non-ISDN terminal device to the ISDN network. Similar to a protocol converter or an interface converter, a TA connects a nonISDN device between the R and S interfaces.
tone dialing—One of two methods of dialing a telephone, usually associated with Touch-Tone® (push button) phones. Compare with pulse dialing.
TSR (terminate and stay resident)—A software program that remains active and in memory after its user interface is closed. Similar to a daemon in UNIX environments.
twisted pair wiring—A type of cabling with one or more pairs of insulated wires wrapped around each other. An inexpensive wiring method used for LAN and telephone applications, also called UTP wiring.
U
Ureference point—A twisted-pair subscriber loop that connects the LT to the NT1. Normally a 2-wire BRI or PRI line is used, but a 4- wire BRI can also be used. In the US, the U Reference Point marks the separation point between CPE and the network.
UART (universal asynchronous receiver/transmitter)—An integrated circuit that transmits and receives data on the serial port. It converts parallel bytes into serial bytes for transmission, and vice versa, and generates and strips the start and stop bits appended to each character.
UTP (unshielded twisted pair) —Telephone-type wiring.
V
V.110—One of the terminal rate adaptation protocols for the ISDN B-channel. V. 110 is more hardware- intensive than the V.120 B-channel standard.
V.120—One of the terminal rate adaptation protocols for the ISDN B-channel. V.120 is more software- intensive than the V. 110 B-channel standard.
Videotex—A two-way information-retrieval service that can be accessed by terminals and by a TV set (with installed decoder). Allows interactive retrieval
of information pages from a central resource. See also ISDN.
virtual circuit—A logical connection. Used in packet switching wherin a logical connection is established between two devices at the start of transmission. All information packets follow the same route and arrive in sequence (but do not necessarily carry a complete address).
x
X.25—ITU-T’s definition of a three-level packet-switching protocol to be used between packet-mode DTEs and network DCEs. X.25 corresponds with layer 3 of the 7-layer OSI model.
X.75—An ITU-T standard for linking X.25 packet-switched networks. X.75 defines the connection between public networks, i.e., for a gateway between X.25 networks.
