T1 Carrier

　　A T1 carrier is a time-division multiplexed digital transmission facility capable of supporting 24 voice channels, (each encoded as a 64 kbps PCM DS0 signal), producing an aggregate multiplexer output signal at the 1.544 Mbps DS1 rate. Developed in the 1960s, the T1 carrier is designed to operate full duplex over two pairs in unshielded twisted pair (UTP) cable.

　　Tandem Switching System

　　A tandem switching system is a broad functional category describing systems that connect trunks to trunks, and route traffic through a network.

　　Tariff

　　A tariff is a published rate for a specific telecommunications service, equipment, or facility that constitutes a public contract between the user and the telecommunications supplier (i.e., carrier); tariff services and rates are established by and for telecommunications common carriers in a formal process in which carriers submit filings for federal or state government regulatory review, public comments, possible amendment, and approval.

　　TA

　　terminal adapter

　　TCP/IP

　　Transmission control protocol/internet protocol. TCP/IP is the transport layer and Internet layer, respectively, of the Internet suite of protocols. TCP corresponds to layer 4 of the OSI protocol stack: IP performs some of the functions of layer 3. It is a connectionless protocol used primarily to connect dissimilar networks to each other.

　　TCP

　　transmission control protocol

　　TDMA

　　time division multiple access

　　TDM

　　time division multiplexing

　　Telecommunications

　　Telecommunications is any process that enables one or more users to pass to one or more other users information of any nature delivered in any usable form, by wire, radio, visual, or other electrical, electromagnetic, optical means. The word is derived from the Greek tele, "far off," and the Latin communicare "to share."

　　Telecommunications Closet

　　In a premises distribution system, a telecommunications closet is an area for connecting the horizontal and backbone wiring and for containing active or passive PDS equipment.

　　Telecommunications Network

　　A telecommunications network is a system of interconnected facilities designed to carry traffic from a variety of telecommunications services. The network has two different but related aspects. In terms of its physical components, it is a facilities network. In terms of the variety of telecommunications services that it provides, it can support a set of many traffic networks, each representing a particular interconnection of facilities.

　　Telecommunications Service

　　Telecommunications service is a specified set of information transfer capabilities provided to a group of users by a telecommunications system.

　　Terrestrial Microwave Radio

　　Terrestrial microwave radio is a transmission systems consisting of at least two radio transmitter/receivers (transceivers) connected to high gain antennas (directional antennas which concentrate electromagnetic or radiowave energy in narrow beams) focused in pairs on each other. The operation is point-to-point, that is, communications are established between two and only two antennas (installations) with line-of-sight visibility. This can be contrasted to point-to- multipoint systems like broadcast radio or television.

　　TIA

　　Telecommunications Industry Association

　　Time Division Multiplexing (TDM)

　　Time Division Multiplexing is a transmission facility shared in time (rather than frequency), i.e., signals from several sources share a single channel or bus by using the channel or bus in successive time slots. A discrete time slot or interval is assigned to each signal source.

　　Time Division Switch

　　A time division switch is a switch that implements the switch matrix using the TDM process, in a time-slot interchange (TSI) arrangement (usually denoted by T in combined time and space division switches).

　　Token Passing Bus LAN (IEEE 802.4)

　　A token passing bus LAN is a LAN using a deterministic accessmechanism and topology in which all stations actively attached to the bus "listen" for a broadcast token or supervisory frame. Stations wishing to transmit must receive the token before doing so; however the next logical station to transmit may not be the next physical station on the bus. Access is controlled by pre- assigned priority algorithms.

　　Token Passing Ring LAN (IEEE 802.5)

　　A token passing ring LAN is a LAN using a deterministic accessmechanism and topology, in which a supervisory frame (or token) is passed from station to adjacent station sequentially. Stations wishing to transmit must wait for the "free" token to arrive before transmitting data. In a token ring LAN the start and end points of the medium are physically connected, leading to a ring topology.

　　TP

　　transaction processing

　　Tracking

　　Tracking features user-defined approval levels and project milestone tables to generate project cost and status information, which is tracked for reporting and review. As assigned tasks are completed, supervisors make daily entries identifying the number of hours worked on a task, materials used, and the number of work units completed. This information is then available for project jeopardy tracking, cost tracking, and termination" title="n.决心；决定">determination of contractor payments due.

　　Traffic

　　Traffic is the flow of information within a telecommunications network.

　　Transceiver

　　A transceiver is a generic term describing a device that can both transmit and receive. In IEEE 802 local area network (LAN) standards, a transceiver consists of a transmitter, receiver, power converter, and, for CSMA/CD LANs, collision detector and jabber detector capabilities. The transmitter receives signals from an attached terminal's network interface card (NIC) and transmits them to the coaxial cable or other LAN medium. The receiver receives signals from the medium and transmits them via the transceiver cable and NIC to the attached terminal. The jabber detector is a timer circuit that protects the LAN from a continuouslytransmitting terminal.

　　Transfer Mode

　　Transfer mode is a generic term for switching and multiplexing aspects of broadband integrated services digital networks (BISDN), adopted by CCITT Study Group XVIII.

　　Transmission control protocol/internet protocol (TCP/IP)

　　See "Internet suite of protocols" and "TCP/IP".

　　Transmission Facilities

　　Transmission facilities provide the communication paths that carry user and network control information between nodes in a network. In general, transmission facilities consist of a medium (e.g., free space, the atmosphere, copper or fiber optic cable) and electronic equipment located at points along the medium. This equipment amplifies (analog systems) or regenerates (digital systems) signals, provides termination functions at points where transmission facilities connect to switching systems, and may provide the means to combine many separate sets of call information into a single "multiplexed" signal to enhance the transmission efficiency.

　　Transmission Impairments

　　Transmission impairments is the degradation caused by practical limitations of channels (e.g., signal level loss due to attenuation, echo, various types of signal distortion, etc.), or interference induced from outside the channel (such as power-line hum or interference from heavy electrical machinery).

　　Transmission Medium

　　Transmission medium is any material substance or "free space" (i.e., a vacuum) that can be, or is, used for the propagation of suitable signals, usually in the form of electromagnetic (including light waves), or acoustic waves, from one point to another; unguided in the case of free space or gaseous media or guided by a boundary of material substance.

　　Transport Services

　　Transporrt Services are networkswitching, transmission and related services that support information transfer capabilities between originating and terminating access service facilities.

　　Trunk

　　In a network, a trunk is a communications path connecting two switching systems used to establish end-to-end connections between customers.

　　Twisted Pair

　　Twisted pair is the most common type of transmission medium, consisting of two insulated copper wires twisted together. The twists or lays are varied in length to reduce the potential for interference between pairs. In cables greater than 25 pair, the twisted pairs are grouped and bound together in a common cable sheath. See unshielded twisted pair.

　　T-1 - A leased line connection that can carry 1,544,000 bits per second.

　　T-3 - A leased line connection that can carry 44,736,000 bits per second.

　　Tariff - Documents filed by a telephone company with a state public utilitycommission and the FCC describing its services and the payments to be charged for the services.

　　TCP/IP - See Transmission Control Protocol/Internet Protocol

　　Telecommunications Relay Center Fee/Charge/Surcharge - This state fee helps pay for the relay center that transmits and translates calls for people who are deaf, hard-of-hearing or speech disabled. Mandated nationally by Congress with the passage of the Americans with Disabilities Act, it may also be called "Telecommunication Devices for the Deaf Tax."

　　Telephone Network - The system of wires, fiber-optic cables, satellites and transmission towers that transmit telephone messages from caller to receiver.

　　Telnet - A program that allows Internet users to login to computers other than their host. Telnet also refers to the act of doing so.

　　Text Format vs. HTML Format - Some Web applications, such as e-mail or Web pages, can either be viewed in Text or HTML formats. Text formats generally display only the words (text) in an e-mail or on a Web page and not graphics, such as artwork or photos. HTML format allows display of both text and graphics.

　　Toll Call - A call to any location outside the local service area. Otherwise known as a long distance call.

　　Transmission Control Protocol/Internet Protocol (TCP/IP) - A set of communications protocols or software necessary to access the Internet.

　　Trunk - A communication line between two switching systems. In other words, a telephone line.

　　TTY/TDD - Telephone Typewriter and Telephone Device for the Deaf. A telecommunication device for the hearing impaired using teletypewriter principals. The users call a special operator number and third-party translation.
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