T1 (DS 1) - The digital transmission link consisting of 24 channels to support rates of 1.54 Mb/s.

T3 (DS 3) - The digital transmission link consisting of 672 channels to support rates of 43 Mb/s, each channel supporting 64 kb/s.

tagging - The marking of a message for the purpose of specialized processing or handling on a LAN or internetwork.

tailgating - See piggybacking.

tap - 1. An electrical connection permitting signals to be transmitted onto or off a bus. 2. The linking between the bus and the drop cable that connects the workstation to the bus in 10BASE-5 Ethernet. 3. A device used on community antenna television cables for matching impedance or connecting service drops. See also bridged tap.

taper point - A splice location where the cable size along a route is reduced.

tap-off - See tap.

tapped trunk - A cable connection system where a coaxial cable is tapped by means of a splitter or vampire tap.

teaming - See link aggregation.

telecom hotel - A building that is leased or rented by multiple telecommunications service providers. The building is generally equipped with specialized environmental and power conditioning.

telecommunications - Any transmission, emission, and reception of signs, signals, writings, images, and sounds; that is, information of any nature by cable, radio, optical, or other electromagnetic systems.

telecommunications bonding backbone (TBB) - A copper conductor used to connect the telecommunications main grounding busbar (TMGB) to the telecommunications grounding busbar (TGB) located on the floor farthest away.

telecommunications bonding backbone interconnecting bonding conductor (TBBIBC) - See grounding equalizer.

telecommunications bonding jumper - See bonding conductor for telecommunications.

telecommunications circuit - Links that make it possible for an organizational network to grow beyond the physical boundaries of a building or a campus.

telecommunications closet (TC) - See telecommunications room.

telecommunications drawing - A two dimensional graphic representation of the cabling infrastructure elements for a construction project (e.g., pathways, media types and quantities, work area outlets, telecommunications rooms).

telecommunications enclosure (TE) - 1. A case or housing for telecommunications equipment, cable terminations, and cross-connect cabling. (TIA). 2. A telecommunications space that differs from equipment rooms and entrance facilities in that this space is generally considered a floor-serving or tenant-serving (as opposed to building- or campus-serving) space that provides a connection point between backbone and horizontal cabling.

telecommunications entrance facility (TEF) - See entrance facility (telecommunications).

telecommunications entrance point - See entrance point (telecommunications).

telecommunications entrance room or space - See entrance room or space (telecommunications).

telecommunications equipment bonding conductor (TEBC) - Bonding conductor that should be installed from each piece of equipment in the telecommunications room or equipment room to the telecommunications grounding busbar or telecommunications main grounding busbar.

telecommunications equipment room - See equipment room (telecommunications).

telecommunications grounding busbar (TGB) - A common point of connection for telecommunications system and equipment bonding to ground, and located in the telecommunications room or equipment room.

telecommunications infrastructure - See infrastructure (telecommunications).

telecommunications main grounding busbar (TMGB) - A busbar placed in a convenient and accessible location and bonded, by means of the bonding conductor for telecommunications, to the building service equipment (power) ground.

telecommunications media - See media (telecommunications).

telecommunications outlet (TO) - See outlet/connector (telecommunications).

telecommunications outlet/connector - Provides the means for the tenant to connect premises equipment. See also outlet/connector (telecommunications).

telecommunications room (TR) - An enclosed architectural space for housing telecommunications equipment, cable terminations, and cross-connect cabling.

telecommunications service entrance - See entrance facility (telecommunications).

telecommunications space - See space (telecommunications).

Telecommunications Systems Bulletin (TSB) - Document published bytheTelecommunications Industry Association used to provide guidance for design methodologies or installation practices that pertain to telecommunications cabling systems. The next published edition of a related standard typically incorporates these bulletins.

telecommuting - The practice of connecting a remote network device to the organizational network to allow staff to work away from the office.

teleconference - The live exchange of information among persons and machines remote from one another but linked by a telecommunications system.

telemetry - A communications system designed for the automatic transmission of digital or analog data by wire, radio, or other means from remote sources to a receiving source for the recording, monitoring, and analysis of systems.

telephone backboard - An area used for the purpose of cable termination and cross-connection of telecommunications circuits. May be used for cross-connection or interconnection to active equipment or simply as a cross-connection of backbone cabling.

telephone test set - A voice circuit testing device used to identify circuits and perform diagnostics (e.g., butt set).

telephony - 1. Speech transmission by radio sets or telephone sets. 2. Describing telephone equipment and telephone technology.

telescoping pole - A pole used for lifting and moving cable in open ceilings.

temporary cabling - Cables and equipment that are installed to provide service on a temporary basis.

tensile strength - The longitudinal pulling stress needed to break apart a cable or material.

terbo - A suffix that denotes a third version.

terminal (TERM) - 1. A point at which information may enter or leave a telecommunications network. (TIA) 2. A device by means of which wires may be connected to each other.

terminal block (TB) - A protected or unprotected unit that serves to terminate cable conductors and is a transition point between cable conductors.

terminal emulation - The process that enables a personal computer to operate as a terminal for connecting to a mainframe or minicomputer.

terminal mode - A form of remote access where the remote station accesses LAN resources through a specialized terminal server, which makes all requests for LAN resources on behalf of the remote station. Contrast with browser mode, control mode, and transparent mode.

termination - The ending of a transmission or transmission pathway.

termination hardware - Considered to be obsolete. See also connecting hardware.

termination position - A discrete element of connecting hardware where telecommunications conductors are terminated.

terminator - An impedance-matching device placed at the end of the telecommunications transmission line.

terms and conditions (T&C) - A section in a request for quote (RFQ) that defines the terms used in the RFQ and the conditions under which the work must be performed.

test hole - A hale or group of holes dug along a proposed underground route to determine what utilities or other obstructions may be present.

tetrafluoroethylene (TFE) - A thermoplastic material with good electrical insulating properties and chemical and heat resistance.

thimble eye - A device for securing the end of a strand.

thimble eye rod - A device used to place the guy wire(s) within the eye opening when guying from a main pole to a stub pole or when guying to the ground. Also called a thimble eye bolt.

thin client - A device similar to a personal computer with respect to processing power, memory capacity, and graphics capability but lacking removable storage devices.

third generation (3G) mobile telephony - A wireless system intended to provide a global mobility with services including telephony, paging, messaging, Internet, and broadband data. This system provides high-speed data transmissions from 144 kbls to 2 Mb/s. 3G will support multimedia applications (e.g., full-motion video, video conferencing).

threadless fitting - A conduit connector or coupling that does not thread onto the end of the conduit. The compression ring style provides a weatherproof seal.

threat analysis - An evaluation of an environment, structure, or scenario for the purpose of deterring potential vulnerabilities for unauthorized entry, removal of physical or intellectual material, or exposure to terrorist activities.

through penetration - A continuous opening that passes through both surfaces of a fire-rated barrier.

throughput - The amount of data transferred between two points in a given amount of time.

through-window - Refers to transmitting and receiving free space optics signal through glass.

thunderstorm day - Any day thunder is heard at a specific observation point.

tie wrap - Plastic or hook and loop strip used for binding and dressing cable.

tight buffer - A type of cable construction where each fiber is coated with a protective thermoplastic coating to a diameter of 900 microns.

tilt compensator - A variable controlled device used to correct imbalances in video signals.

time division duplex (TDD) - A radio frequency communication scheme that transmits and receives alternately with sequential time slots using a single frequency.

time division multiplexing (TDM) - A transmission technique whereby several low-speed channels are combined into a single high-speed channel for transmission. Each low-speed channel is allocated a specific time position in the bit stream.

time division synchronous code division multiple access (TD-SCDMA) - A third generation mobile telephony standard being developed by the China Academy of Telecommunications Technology in collaboration with Datang and Siemens.

time domain reflectometer (TDR) - A device that sends a signal down a cable, then measures the magnitude and amount of time required for the reflection of that signal to return. TDRs are used to measure the length of cables as well as locate cable faults.

time zone - A specified period of time in which access is allowed.

tip - A means for identification of one conductor of a pair. Historically, associated with the wire connected to the tip portion of an operator's telephone plug. See also ring.

token - A Layer 2 frame containing access control information that is passed from device to device on a token ring, bus, or fiber distributed data interface network.

token bus - An access control method that requires a device to have a token before transmitting its message. Transmissions are in the form of broadcasts that are received by all other devices connected to the network over a logical bus topology.

token passing - An access control method that uses an electronic signal called a token.

token ring - A network protocol in which attached devices share a common cabling system for communications purposes without the possibility of a collision between transmissions. A device is only able to send a message when it is in possession of a special electronic sequence of bits called a token.

tone generator - 1. A device used to apply an analog signal to an electrical conductor for assistance in its identification or to determine its physical or fault location. 2. A device used to generate distinctive audible sounds (tones) for insertion into audio, paging, and telephone systems.

tone probe - A device used to detect an electrically generated signal applied to a cable by a tone generator to assist in identification or fault location. See also tone generator.

top-down design - See functional design process.

topology - The physical or logical arrangement of a telecommunications system. (TIA) See also logical topology and physical topology.

total internal reflection - Confinement of light within an optical fiber because the angle of incidence is within the numerical aperture.

trade size - Name given to materials to identify a nominal size.

traffic prioritization - See prioritization.

traffic shaping - A technique that directs data streams on the basis of their address, protocol, priority, or application content.

trailer - An ending component found in some data packets or frames.

trailer string - Line attached to the end of a cable(s) being pulled. May be used for future additional pulls.

transactional access - The process of providing remote users the means to connect to a LAN to conduct commercial activities. See also content access and resource access.

transceiver - 1. A radio transmitter and receiver combined into a single unit. 2. A device that acts as an interface between the network and the connected device.

transcoding - The process that converts a data transmission between different types of codecs (G.711, G.726, G.729, etc.). This process is used for traditional video conferencing and for video over Internet protocol.

transducer - 1. A specific type of converter (see converter) that changes one form of energy into another. 2. In pressurized systems, a device that permits reading the cable pressure in a pressurized cable.

transfer impedance - A measure of shielding performance determined by the ratio of the voltage on the conductors enclosed by a shield to the surface currents on the outside of the shield.

transition point - 1. A point at the bottom of a wall where a flat undercarpet cable is transitioned to a round unshielded twisted-pair cable. 2. A point where an unlisted cable is transitioned to a listed cable after entering a building.

translational bridge - A networking device capable of converting frame formats from one type to another prior to forwarding messages. Only operates on the logical link control sublayer of the Data Link layer.

translational repeater - A type of repeater used in wireless communications. Translational repeaters regenerate a signal received on one frequency or channel and then retransmit it on another frequency or channel. See also repeater and transponder.

transmission - The movement of information as electrical or optical signals from one point to another via a medium.

transmission budget - The calculated limit for quality service available based on transmission characteristics.

Transmission Control Protocol (TCP) - An Open Systems Interconnection Reference Model Layer 4 connection-oriented protocol. TCP supports reliable, end-toend transmission of data by allowing for guaranteed delivery and sequencing of packets. See also User Datagram Protocol for contrast.

transmission line - A medium used to transport a desired signal between two points.

transmission loss - The decrease in signal that occurs during transmission from one point to another. Expressed in dB.

transmission media - The physical carriers of signal energy radiation (e.g., copper, optical fiber, air). See also media.

transmission medium - See media.

transmission speed - The rate of flow (speed) of binary digit information over a transmission line, expressed in bits per second.

transmit opportunity (TXOP) - Provides a channel access function controlled with a defined starting time and a maximum duration. Access may be obtained by contention or through polling.

transmitter (TX) - Signaling source.

transmitter combiners - A device that allows several transmitters operating in the same frequency range to use a single transmission line and antenna.

transparent bridge - A bridge used in an environment where all ports use the same LAN technology.

transparent mode - A form of remote access where the remote station accesses LAN resources through a remote access server and operates in the same manner as a local station, eliminating the need for a local station.

transponder - 1. A combination uplink receiver and downlink transmitter acting like a repeater. 2. A wireless passive or active communications device that automatically responds to signals picked up.

Transport layer - The Open Systems Interconnection Reference Model layer responsible for providing a level of quality to the message transfer process. Also called Layer 4.

transposed pairs - When two pairs of conductors are terminated in each other's location.

transverse - Lying or extending across or in a cross direction. To pass over, under, or through.

trapeze - A support device using threaded rod and channel stock.

traverse - See transverse.

tree topology - A LAN topology that has only one route between any two nodes on the network. The pattern of connections resembles a tree, or the letter T.

trench duct - An interior or exterior trough embedded in concrete that has removable cover plates level with the top of the surrounding surface. See also header duct.

tri-bit - Three bits; three binary digits.

trim-out - Usually one of the last steps in the home construction process, this is the period when all cables are terminated to the appropriate devices and testing is completed.

triple data encryption standard (3DES) - A version of the data encryption standard using 64 bit keys to encrypt the text message three times using different keys each time.

tri-shielded - A general description for one type of broadband coaxial cable that uses three separate shields under the dielectric outer cable sheath. This type of cable construction is typically used with 75 ohm coaxial cabling.

trough (cable) - A pathway for the containment and protection of cable, typically provided with a removable cover.

trunk cable - Refers to the main distribution cable. A typical trunk cable begins at the headend and terminates at the outermost feeder cable.

trunk coupling unit (TCU) - A unit used to connect a token ring device to the main ring path. It provides the mechanisms for connecting a device to the ring and removing it from the ring in an orderly manner. More commonly called a port.

trunk distribution and feeder - Rigid coaxial cable, typically used for backbone cabling.

trunking - See link aggregation.

T-tap - A device that attaches to a medium used for the purpose of connection to a circuit.

tugger - Device that acts as an assist mechanism for advancing a cable or groups of cables during installation.

tunnel - A virtual private network connection through the Internet.

turnstile - An entryway that uses a mechanical device to restrict entry to one person at a time.

twinaxial - A type of cable described as having two conductors that are insulated from one another, twisted together, surrounded by a common shield, and protected with an outer thermoplastic jacket.

twisted-pair - Two individually insulated copper wires physically twisted together to form a balanced pair.

twisted-pair cable - A multiconductor cable comprising two or more copper conductors twisted in a manner designed to cancel electrical interference. Also called balanced twisted-pair cable.

Twisted-Pair Physical Medium Dependent (TP-PMD) - A network protocol that allows for 100 Mb/s transmission. Another name for ANSI X3.263 standard and copper distributed data interface.

two-level duct - An underfloor raceway system installed with the header raceways and the distribution raceways on two different planes.

two-point method - A method used to measure optical fiber cable loss utilizing two closely spaced cursors on an optical time domain reflectometer.

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