Network Cabling Dictionary 1

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    A B C D E F G H I J K L M N  

A
A	Ampere - A unit of measure of electrical current.
AC	see Alternating Current.
Acceptance Angle	The largest angle that a guided ray of light is accepted by a fiber optic cable.
Access Method	The rules by which a network device gains the rights to transmit a communication on the network. Common methods include carrier sense multiple access with collision detection, token passing, and demand priority.
ACR	see Attenuation Crosstalk Ratio.
Alternating Current	An electric current that cyclically reverses the direction of flow. Frequency is the rate at which a full cycle occurs in one second.
Amplitude	The maximum value of a varying signal.
Amplitude Modulation	One of three basic methods (see also Frequency and Phase Modulation) of adding information to a sine wave signal in which the magnitude of the signal is varied to impose information on it.
ANSI	American National Standards Institute
Analog Signal	An electrical signal that varies continuously without having discrete values (as with a "digital" signal).
AppleTalk	Apple Computer's networking scheme, integrated into most Apple system software, that allows Apple computing systems to participate in peer to peer computer networks and to also access the services of AppleTalk servers. See also LocalTalk.
ARCnet	Attached Resource Computer Network. A relatively low speed form of LAN data link technology (2.5 Mbps) developed by Datapoint, in which all systems are attached to a common coaxial cable. ARCnet uses a token-bus form of medium access control in which a system transmits only when it has the token
Asynchronous	Transmission where sending and receiving devices are not synchronized. Data must carry signals to indicate data division.
Asynchronous Transfer Mode (ATM)	A form of very fast packet switching in which data is carried in fixed length units called "cells". Each cell is 53 bytes in length, with 5 bytes used as a header in each cell. ATM employs mechanisms that can be used to set up virtual circuits between users, in which a pair of users appear to have a dedicated circuit between them. ATM is defined in specifications from the ITU and ATM Forum.
Attachment Unit Interface.	The IEEE 802.3 standard name for the cable connecting an Ethernet transceiver (MAU) to a networked device. An AUI cable is equipped with a 15-pin connector that mates with a 15-pin connector on the networked device.
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.
Attenuation Crosstalk Ratio (ACR)	The difference between attenuation and crosstalk, measured in dB, at a given frequency. A quality factor for cabling to assure that signal sent down a twisted pair is stronger at the receiving end of the cable than any interference imposed on the same pair by crosstalk from other pairs.
Audio	Used to describe the range of frequencies within range of human hearing; approximately 20 to 20,000 Hz.
AUI	see Attachment Unit Interface.
AWG	American Wire Gage - A wire diameter specification. The smaller the AWG number, the larger the wire diameter. Top
B
Backbone	A cable connection between telecommunication or wiring closets, floor distribution terminals, entrance facilities, and equipment rooms either within or between buildings. In star networks, the backbone cable interconnects hubs and similar devices, as opposed to cables running between hub and station. In a bus network, the bus cable.
Back reflection	The light reflected back towards the source from the fiber optic ends and deformations.
Backscattering	Refers to light diffraction at microscopic non-uniformities in the index of refraction of the optical fiber causing back reflection of optical power towards the source.
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.
Balanced Transmission	A mode of signal transmission in which each conductor carries the signal of equal magnitude, but opposite polarity. A 5 volt signal for example, appears as a +2.5 Volts on one conductor and -2.5 Volts on the other.
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".
Band pass	A range of frequencies or wavelengths within which a component operates.
Baseband	A transmission method in which the entire bandwidth of the transmission medium is used to transmit a single digital signal. The signal is driven directly onto the transmission medium without modulation of any kind. Baseband is simpler, cheaper and less sophisticated than Broadband.
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.
Beacon	A special frame in Token-Ring systems indicating a serious problem with the ring such as a break.
BEL	A unit that represents the logarithm of the ratio of two levels.
Bend Loss	A form of increased attenuation in an optical fiber caused by an excessively small bend radius. The attenuation may be permanent if micro fractures caused by the bend continue to affect transmission of the light signal.
Bend Radius	Radius of curvature that a fiber optic or metallic cable can bend before the risk of breakage or increased attenuation occurs.
BER	see Bit Error Rate
BICSI	Building Industry Consulting Service International.
Binder	A tape or thread used to hold assembled cable components in place.
BISDN	Broadband ISDN
Bit	One binary digit.
Bit Error Rate	A measure of data integrity, expressed as the ratio of received bits that are in error, relative to the amount of bits received. Often expressed as a negative power of ten.
Bit Stream	A continuous transfer of bits over some medium.
Bit Stuffing	A method of breaking up continuous strings of 1 bits by inserting a 0 bit. The 0 bit is removed at the receiver.
Bit Time	The length of time required to transmit one bit of information.
BL	Blue.
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.
Bonding	A method used to produce good electrical contact between metallic parts. Also refers to the grounding bars and straps used in buildings to bond equipment to an approved ground.
BPS	Bits per second.
BR	Brown.
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.
BRI	ISDN Basic Rate Interface
Bridged Tap	Multiple appearances of the same cable pair at several distribution points.
Broadband	A transmission facility having a bandwidth sufficient to carry multiple voice, video or data channels simultaneously. Each channel occupies (is modulated to) a different frequency bandwidth on the transmission medium and is demodulated to its original frequency at the receiving end. Channels are separated by "guard bands" (empty spaces) to ensure that each channel will not interfere with its neighboring channels. This technique is used to provide many CATV channels on one coaxial cable.
Broadcast	Sending data to more than one receiving device at a time.
Buffer	A protective coating over a strand of optical fiber.
Bus Topology	1. In general, a physical layout of network devices in which all devices must share a common medium to transfer data, and no two devices may transmit simultaneously. 2. With LANs, a linear network topology in which all computers are connected to a single cable.
Butyl Rubber	A synthetic rubber with good electrical insulating properties.
Byte	A group of 8 bits. Top
C
c	A small "c" is the symbol for the speed of light in a vacuum.
C	A capital "C" is the designation for Celsius.
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.
Campus	The buildings and grounds of a complex, such as a university, college, industrial park or military establishment.
Capacitance	The ability to store electric charge between two conductors separated by a dielectric material. Capacitance is expressed in Farads.
Carrier	An electrical signal of a set frequency that can be modulated in order to carry data.
Carrier Detect	A circuit that detects the presence of a carrier.
Carrier Sense	With Ethernet, a method of detecting the presence of signal activity on a common channel.
Carrier Sense Multiple Access with Collision Detect	A network access method used by Ethernet in which a station listens for traffic before transmitting. If two stations transmit simultaneously, a collision is detected and both stations wait a brief time before attempting to transmit again.
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.
CBX	Computerized Branch Exchange.
Cellular Polyethylene	Expanded or "foam" polyethylene, a material with a reduced dielectric constant consisting of individual closed cells of inert gas suspended in a polyethylene medium.
CDDI	Copper Distributed Data Interface - A version of FDDI that uses copper wire media instead of fiber optic cable.
Channel	The end to end transmission path between two points at which application specific equipment is connected.
Channel Insertion Loss	For fiber optic links, the static loss of a link between a transmitter and receiver. It includes the loss of the fiber, connectors, and splices.
Characteristic Impedance	The impedance that an infinitely long transmission line would have at its input terminal. If a transmission line is terminated in its characteristic impedance, it will appear (electrically) to be infinitely long, thus minimizing signal reflections from the end of the line.
Cheapernet	Another name for thin Ethernet or 10Base2 systems.
Chirping	Refers to the change of optical frequency of laser diodes when the laser diode is pulsed between two different optical power levels. Chirp broadens the laser's spectral width causing chromatic dispersion.
Chromatic Dispersion	Synonym for "material dispersion".
Circuit	1. A system of conducting media designed to pass a signal or voltage between two points. 2. A bi-directional communications path between two pieces of associated equipment.
Cladding	The material surrounding the core of a fiber optic cable. The cladding must have a lower index of refraction than the core in order to contain the light in the core.
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.
Coating	Material surrounding the cladding of the fiber for protection.
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.
Coherence	Refers to the phase stability of two wave trains, from the same optical wave, separated in time
Collision	When electrical signals from two or more devices sharing a common data transfer medium crash into one another. This commonly happens on Ethernet type systems.
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.
Conductivity	The ability of a material to allow the flow of electrical current. It is the reciprocal of resistivity. Measured in "mhos" (ohms backwards).
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.
Core	The central region of an optical fiber through which light is transmitted.
Coupling ratio	The percentage of optical power transferred to the secondary output port of a coupler relative to the total power of the primary and the secondary output ports.
CRC	see Cyclic Redundancy Check
Critical angle	The angle at the interface between core and cladding where a guided ray in the core undergoes total internal reflection.
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 the 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
CSMA/CD	see Carrier Sense Multiple Access with Collision Detect.
Current	The flow of charge in a conductor. See "alternating current" and "direct current".
Current Loop	A two wire transmit/receive interface.
Customer Premises	Buildings, offices, and other structures under the control of a telecommunications customer.
Cutoff Wavelength	A distinct boundary, in the wavelength spectrum, which characterizes the mode of operation of a fiber. A fiber operating at wavelengths lower than the cutoff wavelength is multimode while the same fiber operating at wavelengths higher than cutoff wavelength is single mode.
Cut-through Resistance	The ability of a material to withstand mechanical pressure without damage.
Cyclic Redundancy Check (CRC)	An error checking technique used to ensure the accuracy of transmitting digital code over a communications channel. The transmitted messages are divided into predetermined lengths which, used as dividends, are divided by a fixed divisor. The remainder of the calculation is appended onto and sent with the message. At the receiving end, the computer recalculates the remainder. If it does not match the transmitted remainder, and error is detected. Top
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.
DAS	Dual Attachment Station. Term used with FDDI networks to denote a station that attaches to both the primary and secondary rings.
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.
DC	see Direct Current.
DCE	Data Communications Equipment. Any equipment that connects to Data Terminal Equipment (DTE) to allow transmission between DTEs.
DC Loop Resistance	The total DC resistance of a cable. For twisted pair cable, it includes the round trip resistance, down one wire of the pair and back up the other wire.
Demand Priority	A network access method used by 100VG-AnyLAN. The hub arbitrates requests for network access received from stations, assigning access based on priority and traffic loads.
Demarcation Point	A point where the operational control or ownership changes, such as the point of interconnection between telephone company facilities and a user's building or residence.
DGM	Data Grade Media (see Data Grade)
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 permattivity.
Digital Signal	An electric signal which possesses two distinct states (on/off, positive/negative, one/zero).
Direct Current	An electric current that flows in one direction and does not reverse direction as with "alternating current".
Dispersion	The phenomenon in an optical fiber whereby light photons arrive at a distant point in different phase than they entered the fiber. Dispersion causes receive signal distortion that ultimately limits the bandwidth and usable length of the fiber cable. The two major types of dispersion are 1) mode (or modal) dispersion caused by differential optical path lengths in a multimode fiber, and 2) material dispersion caused by differing transmission times of different wavelengths of light in the fiber optic material.
Distortion	Any undesired change in a wave for or signal.
Distribution Frame	A structure with terminations for connecting the permanent cabling of a facility in a manner that interconnections or cross connects may be readily made.
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.
DS1/DS3	see T1 and T3
DTE	Data Terminal Equipment. Any piece of equipment at which a communications path begins or ends.
Duct	1. A single enclosed raceway for wires or cable. 2. An enclosure in which air is moved.
Duplex	1. (data communications) A circuit used to transmit signals simultaneously in both directions. 2. (general) Two receptacles or jacks in a common housing which accepts two plugs.Top
E
E1/E3	The European versions of T1 and T3. E1 runs at 2.048 Mbps and E3 runs at 34 Mbps.
Earth	A term for zero reference ground.
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 Coupling	The transfer of energy by means of a varying magnetic field. Inductive coupling.
Electromagnetic Field	The combined electric and magnetic field caused by electron motion in conductors.
Electromagnetic Interference	An interfering electromagnetic signal. Network wiring and equipment may be susceptible to EMI as well as emit EMI.
Electrostatic	Electrical charge that exists when the charge is at rest.
Electrostatic Coupling	The transfer of energy by means of a varying electrostatic field. Capacitive coupling.
ELFEXT	Equal Level Far End Crosstalk
EMI	see Electromagnetic Interference.
Encoding	A means of combining clock and data information into a self-synchronized stream of signals.
Entrance Facility	An entrance to a building for both public and private network service cables (including antennae) including the entrance at the building wall and continuing to the entrance room or space.
Entrance Point	The point of emergence of telecommunications conductors through an exterior wall, a concrete floor slab, or from a rigid metal conduit or intermediate metal conduit.
Entrance Room	A space in which the joining of inter- or intra-building telecommunications or networking backbone facilities takes place. An entrance room may also serve as an equipment room.
Equipment Room	An enclosed area housing telecommunications and network equipment, distinguished from the telecommunications or wiring closet by its increased complexity and presence of active equipment.
EPDM	Ethylene-propylene-diene monomer rubber. A material with good insulating properties.
EPR	Ethylene-propylene copolymer rubber. A material with good insulating properties.
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. Top
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.
FCS	Frame Check Sequence. Error detection field.
FDDI	Fiber Distributed Data Interface. An ANSI Standard (ANSI X3T12) for a 100 Mbps token passing network based on fiber-optic (FDDI) and twisted-pair (CDDI) cabling.
Feeder Cable	In a CATV system, the transmission cable from the head end (signal pickup) to the trunk amplifier. Also called a trunk cable.
FEP	Fluorinated ethylene propylene. A thermoplastic with excellent dielectric properties which is often used as insulation in fire rated cables.
FEXT	see Far End Cross Talk
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.
Fillers	Nonconducting components cabled with the insulated conductors or optical fibers to impart roundness, flexibility, tensile strength, or a combination of all three.
Floating	Refers to a circuit that has no connection to ground.
FOIRL	Fiber Optic Inter-Repeater Link. An Ethernet fiber optic connection method intended for connection of repeaters.
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 Division Multiplexing (FDM)	A technique for combining many signals on a single circuit by dividing the available transmission bandwidth by frequency into narrower bands, each used for a separate communication channel.
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. Top
G
G	Green
Gbps	Gigabits per second.
Giga	A prefix meaning one billion
GigaHertz (GHz)	One billion hertz.
GIPOF	Graded Index Plastic Optical Fiber
Graded Index Fiber	A multimode fiber optic cable design in which the index of refraction of the core is lower toward the outside of the core and progressively increases toward the center of the core, thereby reducing modal dispersion of the signal.
Ground	A common point of zero potential such as a metal chassis or ground rod.
Ground Loop	A condition where an unintended connection to ground is made through an interfering electrical conductor. Top
H
Half Duplex Transmission	Data transmission over a circuit capable of transmitting in either direction, but not simultaneously.
HC	see Horizontal Cross Connect.
Head end	The equipment in a cable system which receives the various program source signals, processes them, and retransmits them to subscribers.
Headroom	The amount by which a cable ACR exceeds 10dB.
Hertz	The unit of frequency, one cycle per second (abbreviated Hz).
HF	High Frequency
Home Run	A cable run that connects a user outlet directly with the telecommunications or wiring closet, with no intermediate splices, bridges, taps, or other connections.
Horizontal Cabling, Horizontal Wiring	The portion of the cabling system that extends from the work area outlet to the horizontal cross connect in the telecommunications or wiring closet.
Horizontal Cross Connect	A cross connect of horizontal cabling to other cabling, e.g. horizontal, backbone, or equipment.
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.
HVAC	Heating, ventilation, and air conditioning system.
Hybrid Cable	An assembly of two or more cables (of the same or different types or categories) covered by one overall sheath.
Hypalon	A Dupont trade name for a synthetic rubber (chlorosulfonated polyethylene) used as insulating and jacketing material for cabling. Top
I
I	Symbol used to designate current.
IC	see Intermediate Cross Connect.
ICEA	Insulated Cable Engineers Association
ICS	IBM Cabling System
IDC	Insulation Displacement Contact/Connector
IDF	Intermediate Distribution Frame. This is usually located on each floor within a building. It is tied directly to the Main Distribution Frame via cables.
IEC	International Electro technical Commission
IEEE	Institute of Electrical and Electronics Engineers. A professional organization and standards body. The IEEE Project 802 is the group within IEEE responsible for LAN technology standards.
IEEE 802.1	The IEEE standards committee defining High Level Interfaces, Network Management, Internetworking, and other issues common across LAN technologies.
IEEE 802.2	The IEEE standards committee defining Logical Link Control (LLC).
IEEE 802.3	The IEEE standards committee defining Ethernet networks.
IEEE 802.5	The IEEE standards committee defining Token-Ring standards.
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.
Impedance Matching Transformer	A transformer designed to match the impedance of one circuit to another.
Index of Refraction	The ratio of light velocity in a vacuum to its velocity in a given transmission medium.
Infrastructure, Telecommunications	A collection of those telecommunications components, excluding equipment, that together provide the basic support for the distribution of all information within a building or campus.
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.
Intermediate Cross Connect	A cross-connect between 1st level and 2nd level backbone cabling.
Injection Laser Diode	A semiconductor laser in which the lasing occurs at the junction of n-type and p-type semiconductor materials.
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).
ISDN	Integrated Services Digital Network
ISO	International Standards Organization
Isolated Ground	A separate ground conductor which is insulated from the equipment or building ground.
Isolation	The ability of a circuit or component to reject interference.
Insulation	A material which is nonconductive to the flow of electrical current.
Interference	Undesirable signals which interfere with the normal operation of electronic equipment or electronic transmission.
Isochronous	Signals which are dependent on some uniform timing or carry their own timing information imbedded as part of the signal. Voice and video signals are isochronous signals, but data transfer is generally not.
ITU	International Telecommunications Union. An international organization that develops communications standards. Top
J
Jabber	Term used with Ethernet to describe the act of continuously sending data. A jabbering station is one whose circuitry or logic has failed, and which has locked up a network channel with its incessant transmission.
Jack	A female connector.
Jacket	The outer protective covering of a cable.
Jitter	The slight movement of a transmission signal in time or phase that can introduce errors and loss of synchronization. More jitter will be encountered with longer cables, cables with higher attenuation, and signals at higher data rates. Also, called phase jitter, timing distortion, or intersymbol interference.
Jumper	An assembly of twisted pairs without connectors used to used to join telecommunications circuits at the cross connect. Similar to a patch cable (which has connectors). Top
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. Top
L
L	Symbol used to designate inductance.
LAN	Local Area Network
LAN Adapter	see Network Interface Card
Laser	Light Amplification by Stimulated Emission of Radiation. A device which produces light with a narrow spectral width. Used in fiber optic communication systems, usually single mode, where high capacity and low attenuation are required.
LATA	Local Access and Transport Area.
Lay	The axial distance required for one cabled conductor or conductor strand to complete one revolution about the axis around which it is cabled.
Lay Direction	The direction of the progressing spiral twist in while looking along the axis of the cable away from the observer. The lay direction can be either "left" or "right".
LCL	see Longitudinal Conversion Loss
LCTL	see Longitudinal Conversion Transfer Loss
Leakage	An undesirable passage of current over the surface of or through a connector.
Leased Line	A private telephone line rented for the exclusive use of a leasing customer, without interchange switching arrangements.
LED	see Light Emitting Diode.
LF	Low frequency.
Light Emitting Diode	A semiconductor diode which emits incoherent light when a current is passed through it. Used as a light source in fiber optic transmission.
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.
Lobe	An arm of a Token-Ring which extends from a Multistation Access Unit (MSAU) to a workstation adapter.
LocalTalk	A low-speed form of LAN data link technology, part of Apple Computer's AppleTalk networking scheme, that uses a carrier sense multiple access with collision avoidance (CSMA/CA) form of medium access control. Supports transmission at 230 Kbps.
Longitudinal Conversion Loss (LCL)	Also called near-end unbalance attenuation, measures cable balance by comparing the signal appearing across the pair to the signal applied between ground and the pair, where the applied signal and the across pair signal are at the same end of the cable.
Longitudinal Conversion Transfer Loss (LCTL)	Also called far-end unbalance attenuation, measures cable balance by the comparison of the signal appearing across the pair to the signal between ground and the pair, where the applied signal is at the opposite end of the cable from where the across pair signal is measured.
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.
Loss	The portion of energy applied to a system that is dissipated and performs no useful work.
Lossy	Having poor efficiency. Top
M
M	Mutual Inductance
mA	Milliampere (one thousandth of an ampere)
MAC	see Medium Access Control
Main Cross Connect	A cross connect for first level backbone cables, entrance cables, and equipment cables. The main cross connect is at the top level of the premises cabling tree.
Manchester Coding	A method of LAN signal encoding in which each bit time that represents a data bit has a transition in the middle of the bit time. Used with 10 Mbps Ethernet (10Base2, 10Base5, 10Base-F, & 10Base-T), and Token-Ring LANs.
Material Dispersion	Dispersion that results from each wavelength traveling at a different speed than other wavelengths through an optical fiber. Also called "chromatic dispersion".
MAU	Media Attachment Unit. The transceiver in Ethernet networks. Also a common name for the MSAU (Multi-station Access Unit) in Token-Ring networks.
Mbaud	Megabaud. One million baud.
Mbps	Megabits per second.
MC	see Main Cross Connect
MDF	Main Distribution Frame
MDI	see Media Dependent Interface
Media	Wire, cable, or conductors used for transmission of signals.
Media Filter	An impedance matching component used in Token-Ring networks to transform the 100 ohm impedance of UTP cabling to the 150 ohm impedance of media interface connections.
Medium Access Control (MAC)	A mechanism operating at the data link layer of local area networks which manages access to the communications channel (medium).
Medium Dependent Interface (MDI)	In Ethernet, the connector used to make the mechanical and electrical interface between a transceiver and a media segment. An 8-pin RJ-45 connector is the MDI for the 10Base-T, 100Base-TX, 100Base-T2, 100Base-T4, and 1000Base-T media systems.
Medium Independent Interface (MII)	Used with 100 Mbps Ethernet systems to attach MAC level hardware to a variety of physical media systems. Similar to the AUI interface used with 10 Mbps Ethernet systems. An MII provides a 40-pin connection to outboard transceivers (also called PHY devices).
Mega	Prefix meaning one million.
Megahertz (MHz)	One million hertz.
MIC	Medium Interface Connector. Duplex fiber optic connector used with Fiber Distributed Data Interface (FDDI) networks.
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.
Midsplit Broadband	A broadcast network configuration in which the cable is divided into two channels, each using a different range of frequencies. One channel is used to transmit signals and the other is used to receive.
MII	see Medium Independent Interface.
Mil	Unit of length equal to one thousandth of an inch (0.001 inch).
Milli	Prefix meaning one thousandth.
Mixing Segment	Ethernet term used in IEEE 802.3 standards to describe a segment that may have more than two MDI connections.
MMF	set Multimode Fiber
Modal Dispersion	Dispersion that results from the different transit lengths of different propagating modes in a multimode optical fiber.
Mode	A single electromagnetic wave traveling in an optical fiber.
Mode Field Diameter	The diameter of optical energy in a single mode fiber. Because the mode-field diameter is larger than the core diameter, it replaces core diameter as a practical parameter.
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.
MSAU	Multi-station Access Unit. Device used to interconnect lobe cables from stations on a Token-Ring network.
MT-RJ	Proposal for a new duplex fiber optic connector standard from AMP/Siecor.
Multimode Fiber	A fiber optic cable which supports the propagation of multiple modes. Multimode fiber may have a typical core diameter of 50 to 100 µm with a refractive index that is graded or stepped. It allows the use of inexpensive LED light sources and connector alignment and coupling is less critical than single mode fiber. Distances of transmission and transmission bandwidth are less than with single mode fiber due to dispersion.
Mutual Capacitance	Capacitance between two conductors when all other conductors are connected together.
mV	Millivolt (one thousandth of a volt)
mW	Milliwatt (one thousandth of a watt)
Mylar	Dupont trademark for polyethylene terephtalete (polyester) film.
N
NA	see Numerical Aperture
N connector	A coaxial connector used for Ethernet 10Base5 thick coax segments.
Nanometer (nm)	One billionth of a meter.
Nanosecond (ns)	Butadiene-acrylonitrile copolymer rubber, a material with good oil and chemical resistance.
NBR	One billionth of a second.
Near-End Crosstalk	Crosstalk between two twisted pairs measured at the same end of the cable as the disturbing signal source. NEXT is the measurement of interest for crosstalk specifications.
NEC	National Electrical Code.
NEMA	National Electrical Manufacturers Association.
Neoprene	A synthetic rubber with good resistance to oil, chemical, and flame. Also called polychloroprene.
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).
NEXT	see Near-End Crosstalk.
NFPA	National Fire Protection Association
Nibble	One half byte.
NIC	see Network Interface Card.
NIR	Near-end Crosstalk-to-Insertion Loss Ratio
Node	End point of a network connection. Nodes include any device connected to a network such as file servers, printers, or workstations.
Noise	In a cable or circuit, any extraneous signal which interferes with the desired signal.
Nomex	Dupont trademark for a temperature-resistant, flame retardant nylon.
NRZ	Non Return to Zero.
NRZI	Non Return to Zero Inverted.
Numerical Aperture (NA)	The "light gathering ability" of an optical fiber, defining the maximum angle to the fiber axis at which light will be accepted and propagated.
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.
Nylon	An abrasion resistant thermoplastic with good chemical resistance. Top

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