Glossary T0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
0-A | B | C-Cn | Co-Cz | D | E | F-G | H-I | J-L | M | N-O | P-Q | R | S | T | U-Z
- 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
- T1: A 1.544 megabits per second multichannel
transmission system for voice or data provided by long-distance
- 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
- Tap: A device in the feeder cable that connects a device
to a network.
- TCP: See Transmission Control
- TCP/IP: Transmission Control
Protocol/Internet Protocol) A protocol suite
developed by ARPA.
- TDM: See Time Division
- Technical Office Protocol: (TOP) A
version of the OSI (Open Systems Interconnection) model for the office
developed by Boeing.
- Teflon: DuPont Company trademark for
- 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
- Telnet: TCP/IP protocol governing character-oriented
- 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.
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
- 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
- TFE: See Tetraflouroethylene
- Thermal Rating: The temperature
range in which a material will perform its function without undue
- Thermoplastic: A material which will soften, flow or
distort appreciably when subjected to sufficient heat &
- Thermosetting: A material which will not soften, flow, or
distort appreciably when subjected to heat & pressure,
- Thicknet: Cabling scheme using "trunk" cable with
- Thin Ethernet: An IEEE 802.3
LAN(10Base-2) that utilizes RG58-type (50 ohm) stranded coaxial
- 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
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
- 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
- Time Slicing: Dividing a resource so that each application or
task that requests the resource is allocated some amount of
- 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
- 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
- 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
- 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
- Token Bus: A bus topology network using a token passing
- 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 &
- 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
- Transmission Block: A sequence of continuous
, characters or bits transmitted a unit.
Control Protocol: (TCP) TCP/IP protocol governing sequenced
- Transmission Line: An arrangement of two or more conductors or
a waveguide used to transfer signal energy from one location to
- Transmission Medium: The physical mechanism that allows for
signals to be passed from one data communications device to
- 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
- 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
- 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
- Triggers: Uncompiled code reside on an intelligent database
- 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
- 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
- Type 1 cable: Shielded two-pair cable.
- Type 3 cable:
Unshielded twisted-pair cable.