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GLOSSARY OF TERMS
A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z
A
ANSI : American National Standards Institute
Analog Signal : An electrical signal that varies continuously without having discrete values (as with a "digital" signal).
Attenuation : The decrease in magnitude of a signal as it travels through any transmission medium such as a cable or optical fiber. Measured in dB per unit of length.
Audio : Used to describe the range of frequencies within range of human hearing; approximately 20 to 20,000 Hz.
AS-9100 : A quality system developed by the aerospace industry containing standards for best practices in manufacturing and designing aerospace equipment.
AWG : American Wire Gage - A wire diameter specification. The smaller the AWG number, the larger the wire diameter.
B
Balanced Cable, Balanced Line : A cable having two identical conductors that carry voltages of opposite polarities and equal magnitude with respect to ground. The conductors are twisted to maintain balance over a distance.
Balun : An impedance matching transformer that converts the impedance of one interface to the impedance of another interface. Generally used to connect balanced twisted pair cabling with unbalanced coaxial cabling. The term is derived from "balanced / unbalanced".
Bandwidth : The range of frequencies required for proper transmission of a signal. Expressed in Hertz (cycles per second). The higher the bandwidth, the more information that can be carried. A continuous range starting from zero is said to be "baseband", while a range starting substantially above zero is "broadband".
Baud : The number of changes in signal per second. A given baud rate does not necessarily transmit an equal number of bits/sec. For example, a signal with four voltage levels may be used to transfer two bits of information for every baud.
Bend Radius : Radius of curvature that a fiber optic or metallic cable can bend before the risk of breakage or increased attenuation occurs.
Binder : A tape or thread used to hold assembled cable components in place.
BNC : A coaxial connector that uses a "bayonet" style turn and lock mating method. Used with RG-58 or smaller coaxial cable. Used with 10Base2 Ethernet thin coaxial cable. BNC is an acronym for Bayonet-Neill-Concelman.
Braid : Fine wires interwoven to form a tubular flexible structure that may be applied over one or more wires for the purpose of shielding. May also be formed into a flattened conductor to be used as a grounding strap
C
Cable : A group of insulated conductors enclosed within a common jacket.
Cable Sheath : A covering over the conductor assembly that may include one or more metallic members, strength members or jackets.
Capacitance : The ability to store electric charge between two conductors separated by a dielectric material. Capacitance is expressed in Farads.
Category 1, Cat 1 : Unshielded twisted pair used for transmission of audio frequencies. Used as speaker wire, door bell wire, etc. Not suitable for networking applications.
Category 2, Cat 2 : Unshielded twisted pair used for transmission at frequencies up to 1.5 Mhz. Used in analog telephone applications. Not suitable for networking applications.
Category 3, Cat 3 : Unshielded twisted pair with 100 ohm impedance and electrical characteristics supporting transmission at frequencies up to 16 MHz. Defined by the TIA/EIA 568-A specification.
Category 4, Cat 4 : Unshielded twisted pair with 100 ohm impedance and electrical characteristics supporting transmission at frequencies up to 20 MHz. Defined by the TIA/EIA 568-A specification.
Category 5, Cat 5 : Unshielded twisted pair with 100 ohm impedance and electrical characteristics supporting transmission at frequencies up to 100 MHz. Defined by the TIA/EIA 568-A specification.
Category 5e, Cat 5e, Enhanced Cat 5, Cat 5+ : Category 5e is a new standard that will specify transmission performance that exceeds Cat 5. Cat 5e has improved specifications for NEXT, PSELFEXT, and Attenuation. Like Cat 5, it consists of unshielded twisted pair with 100 ohm impedance and electrical characteristics supporting transmission at frequencies up to 100 MHz. To be defined in the TIA 568-A-5 update.
Category 6, Cat 6 : Category 6 is a proposed standard that aims to support transmission at frequencies up to 250 MHz over 100 ohm twisted pair.
Category 7, Cat 7 : Category 7 is a proposed standard that aims to support transmission at frequencies up to 600 MHz over 100 ohm twisted pair.
CATV : Community antenna television, or "Cable TV". CATV is a broadband transmission facility which generally uses a 75 Ohm coaxial cable to carry numerous frequency-divided TV channels simultaneously.
CDDI : Copper Distributed Data Interface - A version of FDDI that uses copper wire media instead of fiber optic cable.
Class A : ISO/IEC 11801 designation for twisted pair cabling rated to 100 KHz. Used in voice and low frequency applications. Comparable to Category 1 cabling. Not suitable for networking applications
Class B : ISO/IEC 11801 designation for twisted pair cabling rated to 1 MHz. Used in medium bit rate applications. Comparable to Category 2 cabling. Not suitable for networking applications
Class C : ISO/IEC 11801 designation for twisted pair cabling rated to 16 MHz. Used in high bit rate applications. Corresponds to TIA/EIA Category 3 cabling.
Class D : ISO/IEC 11801 designation for twisted pair cabling rated to 100 MHz. Used in very high bit rate applications. Corresponds to TIA/EIA Category 5 cabling.
Class E : ISO/IEC proposal for twisted pair cabling rated to 250 MHz. Corresponds to the proposed TIA/EIA Category 6 cabling standard.
Closet : An enclosed space for housing telecommunications and networking equipment, cable terminations, and cross-connect cabling. It contains the horizontal cross connect where the backbone cable cross-connects with the horizontal cable.
Coax, Coaxial Cable : A type of communication transmission cable in which a solid center conductor is surrounded by an insulating spacer which in turn is surrounded by a tubular outer conductor (usually a braid, foil or both). The entire assembly is then covered with an insulating and protective outer layer. Coaxial cables have a wide bandwidth and can carry many data, voice and video conversations simultaneously.
Conduit : A rigid or flexible metallic or nonmetallic raceway of circular cross section in which cables are housed for protection and to prevent burning cable from spreading flames or smoke in the event of a fire.
Conductor : A material that offers low resistance to the flow of electrical current.
Continuity : An uninterrupted pathway for electrical signals.
Cord : A very flexible insulated cable.
Cross Connect : A facility enabling the termination of cable elements and their interconnection, and/or cross-connection, primarily by means of a patch cord or jumper.
Cross Connection : A connection scheme between cabling runs, subsystems, and equipment using patch cords or jumpers that attach to connecting hardware at each end.
Crossover : A conductor which connects to a different pin number at each end.
Crossover Cable : A twisted pair patch cable wired in such a way as to route the transmit signals from one piece of equipment to receive signals of another piece of equipment, and vice versa.
Crosstalk : The coupling of unwanted signals from one pair within a cable to another pair. Crosstalk can be measured at the same (near) end or far end with respect to the signal source.
CSA : Canadian Standards Association
D
D Connector : see Subminiature D Connector
Data Connector : A four position connector for 150-ohm STP used primarily with Token-Ring networks.
Data Grade : A term used for twisted-pair cable used in networks to carry data signals. Data grade media has a higher frequency rating than voice grade media used in telephone wiring.
dB : Decibel. A unit for measuring the relative strength of a signal. Usually expressed as the logarithmic ratio of the strength of a transmitted signal to the strength of the original signal. A decibel is one tenth of a "bel".
DB-9 : Nine pin D connector.
DB-15 : Fifteen pin D connector.
DB-25 : Twenty-five pin D connector.
Dielectric : An insulating (non-conducting) material.
Dielectric Constant : The property of a dielectric which determines the amount of electrostatic energy that can be stored by the material when a given voltage is applied to it. Also called permittivity.
Digital Signal : An electric signal which possesses two distinct states (on/off, positive/negative, one/zero).
DIW : Direct Inside Wire. Twisted pair wire used inside a building, usually two or four pair AWG 26.
Drain Wire : An uninsulated wire in contact with a shield throughout its length. Used to terminate the shield.
Drop Cable : The cable which allows connection and access to and from the trunk cables of a network such as the cables that connect individual PCs to the bus on a bus LAN. In a CATV system, the transmission cable from the distribution cable to a dwelling.
Duct : A single enclosed raceway for wires or cable. An enclosure in which air is moved.
Duplex : A circuit used to transmit signals simultaneously in both directions. Two receptacles or jacks in a common housing which accepts two plugs.
E
EC : European Community
ECMA : European Computer Manufacturer's Association. A European trade organization that issues its own standards and is a member of the ISO.
EIA : Electronic Industry Association (formerly RMA or RETMA). An association of manufacturers and users that establishes standards and publishes test methodologies.
Electromagnetic Interference (EMI): An interfering electromagnetic signal. Network wiring and equipment may be susceptible to EMI as well as emit EMI.
Ethernet : A local area network (LAN) protocol defined in the IEEE 802.3 standard in which computers access the network through a Carrier Sense Multiple Access / Collision Detect (CSMA/CD) protocol.
F
F : Frequency
Farad : A unit of capacitance that stores one coulomb of electrical charge when one volt of electrical pressure is applied.
Far End Cross Talk (FEXT) : Crosstalk that is measured on the quiet line at the opposite end as the source of energy on the active line. FEXT is not typically measured in cabling, with Near End Cross Talk (NEXT) being the preferred crosstalk measurement.
Fast Ethernet : Ethernet standard supporting 100 Mbps operation.
FCC : Federal Communications Commission.
Feeder Cable : In a CATV system, the transmission cable from the head end (signal pickup) to the trunk amplifier. Also called a trunk cable.
Fiber Optics : The technology in which communication signals in the form of modulated light beams are transmitted over a glass fiber transmission medium. Fiber optic technology offers high bandwidth, small space needs and protection from electromagnetic interference, eavesdropping and radioactivity.
Fifty-pin Connector : Commonly referred to as a Telco, CHAMP, or blue ribbon connector, this connector is used on Ethernet 10Base-T hubs as an alternate twisted-pair segment connection method. The 50-pin connector connects to 25-pair cables, which are frequently used in telephone wiring systems and which typically meet Category 3 specifications.
Frequency : The number of times a periodic action occurs in a unit of time. Expressed in hertz (abbreviated Hz). One hertz equals one cycle per second.
Frequency Modulation (FM) : One of three basic methods (see also Amplitude and Phase Modulation) of adding information to a sine wave signal in which its frequency is varied to impose information on it.
Frequency Response : The range of frequencies over which a device operates as expected.
FTP : see Screened Twisted Pair (ScTP) cable
Full Duplex Transmission : Data transmission over a circuit capable of transmitting in both directions simultaneously.
G
Gbps : Gigabits per second.
Giga : A prefix meaning one billion
Gigahertz (GHz) : One billion hertz.
Ground : A common point of zero potential such as a metal chassis or ground rod.
H
Hertz : The unit of frequency, one cycle per second (abbreviated Hz).
HF : High Frequency
Host : Computer that offers services on a network.
Hub : A hardware device that contains multiple independent but connected modules of network and internetworking equipment. Hubs can be active (where they repeat signals set to them) or passive (where they do not repeat but merely split signals sent through them). Hub may also refer to a repeater, bridge, switch, router, or any combination of these.
Hybrid Cable : An assembly of two or more cables (of the same or different types or categories) covered by one overall sheath.
I
ICEA : Insulated Cable Engineers Association
ICS : IBM Cabling System
IDC : Insulation Displacement Contact/Connector
IEC : International Electrotechnical Commission
IEEE : Institute of Electrical and Electronics Engineers. A professional organization and standards body.
Impedance : A unit of measure, expressed in Ohms, of the total opposition (resistance, capacitance and inductance) offered to the flow of an alternating current.
Impedance Match : A condition where the impedance of a particular circuit cable or component is the same as the impedance of the circuit, cable, or device to which it is connected.
Interconnection : A connection scheme that provides for the direct connection of a cable to another cable or to an equipment cable without a patch cord or jumper.
Insertion Loss : A measure of the attenuation of a device by determining the output of a system before and after the device is inserted into the system. For example, a connector causes insertion loss across the interconnection (in comparison to a continuous cable with no interconnection).
IPC-610 : Standards developed to identify best practices and quality for the circuit board manufacturing industry.
IPC-620 : Standards developed to identify best practices and quality for the cable manufacturing industry
ISDN : Integrated Services Digital Network
ISO : International Standards Organization
Isolated Ground : A separate ground conductor which is insulated from the equipment or building ground.
ITU : International Telecommunications Union. An international organization that develops communications standards.
J
Jack : A female connector.
Jacket : The outer protective covering of a cable.
Jumper : An assembly of twisted pairs without connectors used to join telecommunications circuits at the cross connect. Similar to a patch cable (which has connectors).
K
Keying : The mechanical feature of a connector system that guarantees correct orientation of a connection, or prevents the connection to a jack, or to an optical fiber adapter, of the same type intended for another purpose.
L
LAN : Local Area Network
Link : A transmission path between two points not including terminal equipment, work area cables, or equipment cables.
Listed : Equipment included on a list published by an organization, acceptable to the authority having jurisdiction, that maintains periodic inspection of production of listed equipment, and whose listing states either that the equipment or material meets appropriate standards or has been tested and found suitable for use in a specified manner.
Loopback : A type of diagnostic test in which a transmitted signal is returned to the sending device after passing through a data communications link or network. This test allows the comparison of a returned signal with the transmitted signal.
M
mA : Milliampere (one thousandth of an ampere)
Mbps : Megabits per second.
Media : Wire, cable, or conductors used for transmission of signals.
Mega : Prefix meaning one million.
Megahertz (MHz) : One million hertz.
Micro : Prefix meaning one millionth.
Microfarad : One millionth of a farad. Abbreviated µF (less commonly µfd, mf, and mfd).
Micron : One millionth of a meter. Abbreviated µm.
Mil : Unit of length equal to one thousandth of an inch (0.001 inch).
Milli : Prefix meaning one thousandth.
Modem : A device that implements "modulator-demodulator" functions to convert between digital data and analog signals.
Modular Jack : The equipment mounted half of a modular interconnection. Typically a female connector. A modular jack may be keyed or unkeyed and may have six or eight contact positions, but not all the positions need to be equipped with jack contacts.
Modular Plug : The cable mounted half of a modular interconnection. Typically a male connector. A modular plug may be keyed or unkeyed and may have six or eight contact positions, but not all the positions need to be equipped with contacts.
Modulation : Altering the characteristics of a carrier wave to convey information. Modulation techniques include amplitude, frequency, phase, plus many other forms of digital encoding.
Mutual Capacitance : Capacitance between two conductors when all other conductors are connected together.
N
N connector : A coaxial connector used for Ethernet 10Base5 thick coax segments.
Nanometer (nm) : One billionth of a meter.
Nanosecond (ns) : One billionth of a second.
NEC : National Electrical Code.
NEMA : National Electrical Manufacturers Association.
Network : An interconnection of computer systems, terminals or data communications facilities.
Network Interface Card : A circuit board installed in a computing device used to attach the device to a network. A NIC performs the hardware functions that are required to provide a computing device with physical communications capabilities. Also Network Interface Unit (NIU).
Noise : In a cable or circuit, any extraneous signal which interferes with the desired signal.
NVP : Nominal Velocity of Propagation. The speed a signal propagates through a cable expressed as a decimal fraction of the speed of light in a vacuum.
O
Octet : 8 bits (also called a byte).
Ohm : The electrical unit of resistance. The value of resistance through which a potential of one volt will maintain a current of one ampere.
Ohm's Law : Stated E=IR, I=E/R, or R=E/I, the current "I" in a circuit is directly proportional to the voltage "E", and inversely proportional to the resistance "R".
Open : A break in the continuity of a circuit.
Optical Fiber : A thin glass or plastic filament used for the transmission of information via light signals. The signal carrying part of a fiber optic cable.
Optical Fiber Cable : An assembly consisting of one or more optical fibers.
Outlet : A connecting device in the work area on which a horizontal cable terminates.
Outlet Box : A metallic or non-metallic box mounted within a wall, floor, or ceiling used to hold outlet, connector, or transition devices.
Output : The useful signal or power delivered by a circuit or device.
P
Patch Cable, Patch Cord : A flexible piece of cable terminated at both ends with connectors. Used for interconnecting circuits on a patch panel or cross connect.
Patch Panel : A passive device, typically flat plate holding feed through connectors, to allow circuit arrangements and rearrangements by simply plugging and unplugging patch cables.
PC : Personal Computer
PCC : Premises Communication Cable, CSA Cable Designation.
Pico : Prefix meaning one millionth of one millionth.
Picofarad : One millionth of one millionth of a farad. Abbreviated "pf".
Plastic Fiber : An optical fiber made of plastic rather than glass.
Plenum : The air handling space between the walls, under structural floors, and above drop ceilings used to circulate and otherwise handle air in a building. Such spaces are considered plenums only if they are used for air handling. Work spaces are generally not considered plenums.
Plenum Cable : A cable that is rated as having adequate fire resistance and low smoke producing characteristics for use in air handling spaces (plenum).
Plug : A male connector.
PMD : Physical Media Dependent
POF : Plastic Optical Fiber.
Polyvinyl Chloride (PVC) : A general purpose thermoplastic used for wire and cable insulation and plastics. PVC is know for high flexibility. Often used in nonplenum wire insulation and cable jackets. A modified version of the material may be found in jacketing of some plenum rated cables.
Power Ratio : The ratio of power appearing at the load to the input power. Expressed in dB.
Premise Cabling : The entire cabling system on the user's premises used for transmission of voice, data, video and power.
Prewiring : Wiring installed before walls and ceilings are enclosed.
Propagation Delay : Time required for a signal to pass from the input to the output of a device.
Protocol : A set of agree-upon rules and message formats for exchanging information among devices on a network.
Pull Strength, Pull Tension : The pulling force that can be applied to a cable without affecting the specified characteristics of the cable.
Q
R
Raceway : Any channel designated for holding wires or cables. Raceways may be metallic or nonmetallic and may totally or partially enclose the wiring. (e.g. conduit, cable trough, cellular floor, electrical metallic tubing, sleeves, slots, underfloor raceways, surface raceways, lighting fixture raceways, wireways, busways, auxiliary gutters, and ventilated flexible cableways)
Radio Frequency (RF) : The frequencies in the electromagnetic spectrum that are used for radio communications.
Receiver : A device whose purpose is to capture transmitted signal energy and convert that energy for useful functions. In fiber optic systems, an electronic component that converts light energy to electrical energy.
Reflection : A return of electromagnetic energy that occurs at an impedance mismatch in a transmission line, such as a LAN cable.
Refractive Index : The ratio of the speed of light in a vacuum to its velocity in a transmitting medium, such as an optical fiber core.
Repeater : A device that receives, amplifies (and sometimes reshapes), and retransmits a signal. It is used to boost signal levels and extend the distance a signal can be transmitted. It can physically extend the distance of a LAN or connect two LAN segments.
Retractile Cord : A cord having specially treated insulation or jacket so that it will retract like a spring. Retractibility may be added to all or part of a cord's length.
Reversed Pair : A wiring error in twisted pair cabling where the conductors of a pair are reversed between connector pins at each end of a cable.
RFI : Radio Frequency Interference. Electromagnetic interference at radio frequencies.
RFP : Request for Proposal
RFQ : Request for Quote (or Quotation)
RG/U : Radio Grade/Universal. RG is the common military designation for coaxial cable.
Riser : The conduit or path between floors of a building into which telephone, networking, and other utility cables are placed to bring service from one floor to another.
Riser Cable : A type of cable used in vertical building shafts, such as telecommunications and utility shafts. Riser cable typically has more mechanical strength than general use cable and has an intermediate fire protection rating.
RJ : A term from the telephone industry, used for jacks (connectors) that were registered for use with particular types of telephone services. RJ stands for "registered jack".
RJ-45 : A USOC code identifying an 8-pin modular plug or jack used with unshielded twisted pair cable. Officially, an RJ-45 connector is a telephone connector designed for voice grade circuits only. RJ-45 type connectors with better signal handling characteristics are called 8-pin connectors in most standard documents, though most people continue to use the RJ-45 name for all 8-pin connectors.
Rope Strand : A conductor composed of groups of twisted strands.
S
Scanner : A cable testing device which uses TDR methods to detect cable transmission anomalies and error conditions.
Screened Twisted Pair (ScTP) cable : Four pair UTP, with a single foil or braided screen surrounding all four pairs in order to minimize EMI radiation or susceptibility. Screened twisted pair is sometimes called Foil Twisted Pair (FTP). ScTP can be thought of as a shielded version of the Category 3, 4, & 5 UTP cables.
Screened/Shielded Twisted Pair (SSTP) : Four pair cabling, with each pair having its own individual Shield, in addition to an overall shield surrounding all four pairs. SSTP offers similar performance to Type 1 STP except with 4 pairs (rather than 2) and in a 100 ohm impedance (rather than 150).
Semiconductor : In wire industry terminology, a material possessing electrical conductivity that falls somewhere between that of conductors and insulators. Usually made by adding carbon particles to an insulator. Not the same as semiconductor materials such as silicon, germanium, etc.
Shield : A metallic foil or multiwire screen mesh that is used to prevent electromagnetic fields from penetrating or exiting a transmission cable. Also referred to as a "screen".
Shield Coverage : The physical area of a cable that is actually covered by shielding material, often expressed as a percentage.
Shield Effectiveness : The relative ability of a shield to screen out undesirable interference. Frequently confused with the term shield coverage.
Shielded Twisted Pair (STP) : A type of twisted pair cable in which the pairs are enclosed in an outer braided shield, although individual pairs may also be shielded. STP most often refers to the 150 ohm IBM Type 1, 2, 6, 8, & 9 cables used with Token Ring networks.
Signal : The information conveyed through a communication system.
Signal to noise ratio : The ratio of received signal level to received noise level, expressed in dB. Abbreviated S/N. A higher S/N ratio indicates better channel performance.
Silver Satin : The name for the silver-gray voice-grade patch cable used to connect a telephone to a wall jacket. Typical silver satin patch cables do not have twisted pair wires, which makes them unsuitable for use in LAN applications. The lack of twisted pairs will result in high levels of crosstalk.
Simplex Transmission : Data transmission over a circuit capable of transmitting in one preassigned direction only.
Single Mode Fiber (SMF) : An optical fiber that will allow only one mode to propagate. The fiber has a very small core diameter of approximately 8 µm. It permits signal transmission at extremely high bandwidth and allows very long transmission distances.
SMA Connector : A threaded type fiber optic connector. The 905 version is a straight ferrule design, whereas the 906 is a stepped ferrule design.
Source : In fiber optics, the device which converts the electrical information carrying signal to an optical signal for transmission over an optical fiber. A fiber-optic source may be a light emitting diode or laser diode.
Spectrum : Frequencies that exist in a continuous range and have a common characteristic. A spectrum may be inclusive of many spectrums (e.g. the electromagnetic radiation spectrum includes the light spectrum, radio spectrum, infrared spectrum, etc.)
Speed of Light (c) : In a vacuum, 299,800,000 meters per second.
Splice : A joining of conductors generally from separate sheaths.
Splice Closure : A device used to protect a cable or wire splice.
Split Pair : A wiring error in twisted pair cabling where one of a pair's wires is interchanged with one of another pair's wires. Split pair conditions may be determined with a transmission test. Simple DC continuity testing will not reveal the error, because the correct pin-to-pin continuity exists between ends. However, the error may result in impedance mismatch, excessive crosstalk, susceptibility to interference, and signal radiation.
Standing Wave : The stationary pattern of waves produced by two waves of the same frequency traveling in opposite directions on the same transmission line. The existence of voltage and current maxima and minima along a transmission line is a result of reflected energy from an impedance mismatch.
Structural Return Loss (SRL) : A measure of the impedance uniformity of a cable. It measures energy reflected due to structural variations in the cable. A higher SRL number indicates better performance (more uniformity and lower reflections).
Structured Wiring : Telecommunications cabling that is organized into a hierarchy of wiring termination and interconnection structures. The concept of structured wiring is used in the common standards from the TIA and EIA.
Subminiature D Connector : A family of multipin data connectors available in 9, 15, 25 and 37 pin configurations. Sometimes referred to as DB9, DB15, DB25 and DB37 connectors respectively.
Surge : A temporary and relatively large increase in the voltage or current in an electric circuit or cable. Also called transient.
Surge Suppression : The process by which transient voltage surges are prevented from reaching sensitive electronic equipment.
Sweep Test : Pertaining to cable, the frequency response is verified by generating an RF voltage whose frequency is swept repeatedly through a given frequency range at a rapid constant range. The cable response is observed on an oscilloscope. The structural return loss sweep test measures the magnitude of internal cable reflections. A high structural return loss is desirable.
T
Teflon : Dupont Company trademark for flourocarbon resins (see FEP and TFE).
Terminal : 1. A point at which information may enter or leave a communications network. 2. A device by means of which wires may be connected to each other.
Terminator : A device that provides electrical resistance at the end of a transmission line. Its function is to absorb signals on the line, thereby keeping them from bouncing back and being received again by the network.
Thicknet : Ethernet 10Base5 coaxial cable.
Thinnet : Ethernet 10Base2 coaxial cable. Also called "cheapernet".
Time Domain Reflectometry (TDR) : A technique for measuring cable lengths by timing the period between a test pulse and the reflection of the pulse from an impedance discontinuity on the cable. The returned waveform reveals many undesired cable conditions, including shorts, opens, and transmission anomalies due to excessive bends or crushing. The length to any anomaly, including the unterminated cable end, may be computed from the relative time of the wave return and nominal velocity of propagation of the pulse through the cable. See also Optical Time Domain Reflectometry.
TNC : A threaded connector used to terminate coaxial cables. TNC is an acronym for threaded Neill-Concelman.
Transceiver : A combination of the words TRANSmitter and reCEIVER. A transceiver is the set of electronics that send and receive signals on the Ethernet media system. Transceivers may be small outboard devices, or may be built into an Ethernet port. Also called Media Attachment Unit, or MAU.
Tracer : The contrasting color coding stripe along an insulated conductor of a wire pair.
Transmission Media : Anything such as wire, coaxial cable, fiber optics, air or vacuum, that is used to carry a signal.
Transmitter : A device that converts electrical signals for transmission to a distant point. In fiber optic systems, the electronic component that converts electrical energy to light energy.
Triaxial Cable, Triax : Triax cable is coax cable with an additional outer copper braid insulated from signal carrying conductors. It has a core conductor and two concentric conductive shields.
Turn-key : A contractual arrangement in which one party designs and installs a system and "turns over the keys" to another party who will operate the system.
Twinaxial Cable, Twinax : A type of communication transmission cable consisting of two center conductors surrounded by an insulating spacer which in turn is surrounded by a tubular outer conductor (usually a braid, foil or both). The entire assembly is then covered with an insulating and protective outer layer. It is similar to coaxial cable except that there are two conductors at the center.
Twisted Pair : A multiple conductor cable whose component wires are paired together, twisted, and enclosed in a single jacket. Each pair consists of two insulated copper wires twisted together. When driven as a balanced line, the twisting reduces the susceptibility to external interference and the radiation of signal energy. Most twisted-pair cabling contains either 2, 4, or 25 pairs of wires.
Type N Connector : A threaded barrel constant impedance coaxial connector for large diameter cable such as Ethernet 10Base5 thicknet cable.
U
UL : Underwriters Laboratories, Inc.
Unbalanced Line : A transmission line in which voltages on the two conductors are unequal with respect to ground. Generally one of the conductors is connected to a ground point. An example of an unbalanced line is a coaxial cable.
Underground Cable : Cable that is intended to be placed beneath the surface of the ground in ducts or conduit. Not necessarily intended for direct burial in the ground.
Unilay : A conductor with more than one layer of helically laid wires with the direction of lay and length of lay the same for all layers.
Unshielded Twisted Pair (UTP) : Twisted pair cabling that includes no shielding. UTP most often refers to the 100 ohm Category 3, 4, & 5 cables specified in the TIA/EIA 568-A standard.
V
V : Symbol for Volt.
VA : Volt-ampere. A designation of power in terms of voltage and current.
Velocity of Propagation : The transmission speed of electrical energy in a length of cable compared to speed in free space. Usually expressed as a percentage. Test devices use velocity of propagation to measure a signal's transit time and thereby calculate the cable's length.
VGM : Voice Grade Media (see Voice Grade)
VHF : Very high frequency. The portion of the electromagnetic spectrum extending from 30 to 300 MHz.
Video : A signal which contains visual information, such as a picture in a television system.
Voice Grade : A term used for twisted-pair cable used in telephone systems to carry voice signals.
Volt : The unit of electrical potential. One volt is the electrical potential that will cause one ampere of current to flow through one ohm of resistance.
Voltage : Electrical potential expressed in Volts.
Voltage Drop : The voltage developed across a component by the current flow through the resistance of the component.
W
Watt : A unit of electrical power. One watt is equivalent to the power represented by one ampere of current flowing through a load with a voltage drop of one volt in a dc circuit.
Wavelength : The distance between successive peaks or nodes of a wave.
WAN : Wide Area Network. A network connecting computers within very large areas, such as states, countries, and the world.
Workgroup : A collection of workstations and servers on a LAN that are designated to communicate and exchange data with one another.
Workstation : A computer connected to a network at which users interact with software stored on the network.
X
X : Symbol for cross-connect.
Y
Z
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