Glossary T

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  • T-connector: A T-shaped splitter (one connector to two connectors). For example the BNCT is a T-shaped splitter with one female BNC to two female BNCs (BNCT-1M is one male BNC to two female BNCs).
  • T1: A 1.544 megabits per second multichannel transmission system for voice or data provided by long-distance carriers.
  • T3: Term used to denote the type of connection of a host to the Internet. A T3 transmits a Ds-3 formatted digital signal at 44.746 megabits per second.
  • Tap: A device in the feeder cable that connects a device to a network.
  • TCP: See Transmission Control Protocol
  • TCP/IP: Transmission Control Protocol/Internet Protocol) A protocol suite developed by ARPA.
  • TDM: See Time Division Multiplexing
  • Technical Office Protocol: (TOP) A version of the OSI (Open Systems Interconnection) model for the office developed by Boeing.
  • Teflon: DuPont Company trademark for fluorocarbon resins.
  • Telecommunications: Any transmission, emission or reception of sign, signals, writings, images & sounds or information of any nature by wire, radio, visual or other electromagnetic systems.
  • Telecommunications Industries Association: (TIA) The association that creates telecommunications standards through the EIA organization.
  • Telnet: TCP/IP protocol governing character-oriented terminal data.
  • Terminal: Point in a network at which data can either enter or leave; a device, usually equipped with a keyboard, often with a display, capable of sending & receiving data over a communications link; generically the same as data terminal equipment.
  • Terminal Interface Equipment lines: (TIE lines) Long-distance leased lines reserved for the leasing company.
  • Terminated Line: A circuit with a resistance at the far end equal to the characteristic impedance of the line so no reflections or standing waves are present when a signal is entered at the near end.
  • Tetraflouroethylene: (TFE) A thermoplastic material with good electrical insulating properties & chemical & heat resistance.
  • Text: In communications, transmitted characters forming the part of a message that carries information to be conveyed; in some protocols, the character sequence between start-of-text (STX) & end-of-text opposed to computer, comprehension, intended for presentation in a two-dimensional form.
  • TFE: See Tetraflouroethylene
  • Thermal Rating: The temperature range in which a material will perform its function without undue degradation.
  • Thermoplastic: A material which will soften, flow or distort appreciably when subjected to sufficient heat & pressure.
  • Thermosetting: A material which will not soften, flow, or distort appreciably when subjected to heat & pressure, Vulcanizable.
  • Thicknet: Cabling scheme using "trunk" cable with N-type connectors.
  • Thin Ethernet: An IEEE 802.3 LAN(10Base-2) that utilizes RG58-type (50 ohm) stranded coaxial cable.
  • Thread: A processor instruction or series of instructions that make up a complete operation or process & cannot be interrupted or a series of interrelated messages in an on-line conversation.
  • Threshold: Refers to a value set for a resource which if exceeded can result in action being taken by network management.
  • Throughput: The amount of data transmitted between two points in a given amount of time
  • TIA: See Telecommunications Industries Association
  • TIE lines: See Terminal Interface Equipment lines
  • Tight Buffer: Type of cable construction whereby each glass fiber is tightly buffered by a protective thermoplastic coating to a diameter of 900 microns. High tensile strength rating is achieved, providing durability, ease of handling & ease of connecting.
  • Tightly Coupled: A multiprocessor computer in which the CPU's (Central Processing Units) share memory & one system bus.
  • Time Division Multiplexing: (TDM) A method of using channel capacity efficiently, in which each node is allotted a small time internal, in turns, during which it may transmit a message or portion of a message. Nodes are given unique time slots during which they have exclusive command of the channel. The message of many channels are interleaved for transmission & then demultiplexed into their proper order at the receiving end.
  • Time Slicing: Dividing a resource so that each application or task that requests the resource is allocated some amount of time.
  • Time-out: Expiration of predefined time period, at which time some specified action occurs; in communications, time-outs are employed to avoid unnecessary delays & improve traffic flow; used for example, to specify maximum response times to polling & addressing before a procedure is automatically reinitiated.
  • Time-Sharing: A method of computer operation that allows several interactive terminals to use one computer. Although the terminals are actually served in sequence, the high speed of the computer makes it appear as if all terminals were being served simultaneously.
  • Time-To-Live: The maximum time an internet Protocol datagram is allowed to live in the internet before it is dropped to avoid infinite loop forwarding. A router a datagram passes through decrements the Time-to-Live field each time a datagram passes through it. If the field reached zero, the datagram is dropped.
  • Timing Signals: One of the four functional categories of interface signals in the DTE-DCE interface, These signals coordinate the rate at which signal bits are sent & received at the communicating DTE's. Timing signals are primarily used in synchronous transmission.
  • Tinned Copper: Tin coating added to copper to aid in soldering & inhibit corrosion.
  • Tinsel: A type of electrical conductor comprised of a number of tiny threads, each thread having a fine, flat ribbon of copper or other metal closely spiraled about it. Used for small size cables requiring limpness & extra-long flex life.
  • Token: The character sequence passed among nodes in sequence to indicate which one has permission to transmit.
  • Token Bus: A bus topology network using a token passing access method.
  • Token Passing: A LAN technology which employs tokens as part of the access control mechanism.
  • Token Ring: A ring topology LAN that uses the token passing access method.
  • TOP: See Technical Office Protocol
  • Topology: The configuration of a network. The principle network topologies are star, bus, ring & tree.
  • Traffic: The measurement of data movement, volume, & velocity over a communication link.
  • Transaction: In communications, a message destined for an application program; a computer-processed task that accomplishes a particular action or result; in interactive communications, an exchange between two devices, one of which is usually a computer in batch or remote job entry, a job or job step.
  • Transceiver: A combined transmitter & receiver. An essential element of all LANs, its function is required at each node on the network.
  • Transducer: A device for converting mechanical energy to electrical energy
  • Transfer Impedance: For a specified cable length, transfer impedance relates a current on the surface of a shield to the voltage drop generated by this current on the opposite surface of the shield. Transfer impedance is used to determine shield effectiveness against both ingress & engross of interfering signals. Cable shields are normally designed to reduce the transfer of interference-hence, shields with lower transfer impedance are more effective than shields with higher transfer impedance.
  • Transient: An abrupt change in voltage, of short duration for example, a brief pulse caused by the operation of a switch. Also known as Spike.
  • Transmission: The dispatching of a signal, message, or other form of intelligence by wire, radio, telegraphy, telephony, facsimile, or other means a series of characters, messages, or blocks, including control information & user data the signaling of data over communications channels.
  • Transmission Block: A sequence of continuous , characters or bits transmitted a unit.
  • Transmission Control Protocol: (TCP) TCP/IP protocol governing sequenced data.
  • Transmission Line: An arrangement of two or more conductors or a waveguide used to transfer signal energy from one location to another.
  • Transmission Medium: The physical mechanism that allows for signals to be passed from one data communications device to another.
  • Transmitter: The electronic package that converts electrical energy to light energy in a fiber optic system.
  • Transparency: A data communication mode that enables equipment to send & receive bit patterns of any form, without regard to interpretation as control characters. The user is unaware that this is taking place.
  • Transport Layer: Layer 4 of the OSI model; it defines protocols governing message structure & some error checking.
  • Tray: A cable tray system is an assembly of units or sections & ancillary fittings, made of non-combustible materials used to support cables. Cable tray systems include ladders, through, channels, solid bottom trays & similar structures.
  • Tree: A LAN topology with only one route between the nodes of the network.
  • Tree Topology: A network topology in which nodes are connected by cables to a trunk cable with a central retransmission facility.
  • Triaxial: Refers to the three conductor cable with one conductor in the center, a second circular conductor concentric with the first, & a third conductor insulated from & concentric with the first & second, usually with insulation, & a braid or impervious sheath overall.
  • Triggers: Uncompiled code reside on an intelligent database server.
  • Trojan Horse: A program or data that seems innocuous when it is loaded into a system or network but later facilities an attack by a hacker or virus.
  • Trunk: A dedicated aggregate telephone circuit connecting two switching centers, central offices, or data-concentration devices. Also, the main network cable.
  • Trunk Cable: See Feeder Cable
  • Turn-key: A contractual arrangement in which one party designs & installs a system & "turns over the keys" to another party who will operate the system.
  • Twinaxial Cable: A shielded coaxial cable with two central conductors.
  • Twisted Pair: Two insulated wires wrapped around each other.
  • Two-Wire Line: A communication link formed by two wires insulated from each other. The common telephone lines are two-wire lines. Two-wire lines may be used for simplex, half duplex or full-duplex transmission, depending upon the bit rate.
  • Type 1 cable: Shielded two-pair cable.
  • Type 3 cable: Unshielded twisted-pair cable.
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