Ablative – The development of a hard char that resists the erosion of fire and flames; a characteristic of a firestop when exposed to fire.
Access Provider (AP) - a company (eg., telephone company) that provides a circuit path between a service provider (SP) and the client user.
Ampere - A unit of measure of electrical current.
Alternating Current (AC) - 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).
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.
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.
AWG - American Wire Gage - A wire diameter specification. The smaller the AWG number, the larger the wire diameter.
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Backboard – A panel (e.g., wood, metal) used for mounting connecting hardware and equipment.
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.
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".
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.
Bend Radius - Radius of curvature that a fiber optic or metallic cable can bend before the risk of breakage or increased attenuation occurs.
BICSI - Building Industry Consulting Service International.
Bit - One binary digit.
Bit Error Rate (BER) - 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.
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.
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.
Break-out cable – Multifiber cables where each optical fiber is further protected by an additional jacket and optical strength elements.
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. 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.
Byte - A group of 8 bits.
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Cabinet – A container that may enclose connection devices, terminations, apparatus, wiring, and equipment.
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 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 3 - Balanced twisted pair copper cable specifications characterized in a frequency range from 1 to 16 MHz.
Category 4 – The Telecommunications Industry Association no longer recognizes this category.
Category 5 – The Telecommunications Industry Association no longer recognizes this category.
Category 5e – Balanced twisted pair copper cable specifications characterized in a frequency range from 1 to 100 Mhz. This category specified transmission parameters thyat were not characterized by category 5 (e.g., power sum near-end cross talk, return loss, equal level far-end crosstalk, and power sum equal level far-end crosstalk) and features more stringent near-end crosstalk than category 5.
Category 6 - Balanced twisted pair copper cable specifications characterized in a frequency range from 1 to 500 Mhz.
Category 6, Augmented - Balanced twisted pair copper cable specifications characterized in a frequency range from 1 to 500 Mhz. The augmentation from category 6 covers frequency range, insertion loss specifications, and alien crosstalk mitigation.
Category 7 - Balanced twisted pair copper cable specifications characterized in a frequency range from 1 to 600 Mhz.
CATV - Community antenna television, or "Cable TV". CATV is a broadband transmission facility that generally uses a 75 Ohm coaxial cable to carry numerous frequency-divided TV channels simultaneously.
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.
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.
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.
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.
Core - The central region of an optical fiber through which light is transmitted.
Coupling ratio - The percentage of optical power transfered to the secondary output port of a coupler relative to the total power of the primary and the secondary output ports.
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 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.
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.
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D Connector - see Subminiature D Connector
Data Center – A building or portion of a building whose primary function is to house a computer room and it’s support area.
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.
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.
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.
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.
Digital Signal - An electric signal that possesses two distinct states (on/off, positive/negative, one/zero).
Direct Current (DC) - 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.
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.
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.
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Earth - A term for zero reference ground.
Effective Ground – Intentional connection to earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to prevent the buildup of voltages that may result in undue hazards to connected equipment or to persons.
EIA - Electronic Industry Association - 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 (EMI) - 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. Capacitivecoupling.
ELFEXT - Equal Level Far End Crosstalk
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.
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.
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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.
Fault Tolerance– The ability of a system to continue operations after the failure of one or more components or communications paths.
FCC - Federal Communications Commission.
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.
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 – Non-conducting 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.
Full Duplex Transmission - Data transmission over a circuit capable of transmitting in both directions simultaneously.
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Gas Tube Protector – An overvoltage protector featuring metallic electrodes that discharge in a gas atmosphere within a glass or ceramic envelope. This type of protector does not require replacement each time it discharges.
Gbps - Gigabits per second.
Giga - A prefix meaning one billion
Gigahertz (GHz) - One billion hertz.
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.
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Half Duplex Transmission - Data transmission over a circuit capable of transmitting in either direction, but not simultaneously.
Handhole (HH) - A structure similar to a small maintenance hole in which cable can be pulled, but not large enough for a person to fully enter to perform work.
Headend - 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 - 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 (HC) - 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.
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I - Symbol used to designate current.
ICEA - Insulated Cable Engineers Association
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 Electrotechnical 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.
Inductance - A condition that opposes the flow of current while causing a voltage phase shift +90.
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 (IC) - A cross-connect between 1st level and 2nd level backbone cabling.
Innerduct – a nonmetallic raceway, usually circular, placed within a larger pathway.
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.
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.
ITU - International Telecommunications Union. An international organization that develops communications standards.
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Jack - A female connector.
Jacket - The outer protective covering of a cable.
J-hook – A supporting device for horizontal cables that is shaped like a J. It is attached to some building structures. Horizontal cables are laid in the opening formed by the J to provide support for the cables.
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).
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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.
Key Telephone System – multi-line telephone system typically used in small office environments.
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L - Symbol used to designate inductance.
Ladder Cable Tray – A prefabricated structure consisting of side rails connected at the bottom by transverse members (rungs) for supporting and routing cables or conductors within the structure.
LAN - Local Area Network
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.
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.
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.
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M - Mutual Inductance
mA - Milliampere (one thousandth of an ampere)
MAC - see Medium Access Control
Main Cross Connect (MC) - 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.
Maintenance Hole (MH) - A vault located in the ground or earth as part of an underground duct system and used to facilitate placing, connectorization, and maintenance of cables as well as the placing of associated equipment, in which it is expected that a person will enter to perform work.
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".
Mbaud - Megabaud. One million baud.
Mbps - Megabits per second.
MDF - Main Distribution Frame
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 that 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.
Mil - Unit of length equal to one thousandth of an inch (0.001 inch).
Milli - Prefix meaning one thousandth.
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.
MT-RJ - 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)
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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.
Near-End Crosstalk (NEXT) - 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 (NIC) - 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.
NFPA - National Fire Protection Association
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.
Nominal Velocity of Propagation (NVP) – The coefficient used to determine the speed of transmission along a cable relative to the speed of light in a vacuum.
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.
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OFSTP - Optical Fiber Standard Test Procedure.
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".
OLTS - Optical Loss Test Set
Open - A break in the continuity of a circuit.
Open Office – A floor space division provided by furniture, movable partitions, or other means instead of by building walls.
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.
Optical Fiber Duplex Adapter - A mechanical media termination device designed to align and join two duplex connectors.
Optical Fiber Duplex Connection - A mated assembly of two duplex connectors and a duplex adapter.
Optical Fiber Duplex Connector - A mechanical media termination device designed to transfer optical power between two pairs of optical fibers.
Optical Time Domain Reflectometry. - A method for evaluating optical fiber based on detecting and measuring backscattered (reflected) light. Used to measure fiber length and attenuation, evaluate splice and connector joints, locate faults, and certify cabling systems.
OSI - Open Systems Interconnection
Outside Plant - Cabling, equipment, or structures that are out of doors.
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.
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Packet - Bits grouped serially in a defined format, containing a command or data message sent over a network.
PAM5x5 - Signal encoding scheme used in the Ethernet 100Base-T2 and 1000Base-T media systems.
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.
Pathway - A facility for the placement of telecommunication or networking cables.
PBX - Private Branch Exchange
PC - Personal Computer
PCC - Premises Communication Cable
PDN - Public Data Network
Peak - The maximum instantaneous value of a varying current or voltage.
Pedestal - A device, usually mounted on the floor, which is used to house voice/data jacks or power outlets at the point of use. Also referred to as a monument, tombstone,
above floor fitting or doghouse.
Penetration – Opening made in a firestop barrier.
Periodicity - Uniformly spaced variations in the insulation diameter of a transmission cable that result in reflections of a signal.
Phase - An angular relationship between waves.
Phase Modulation (PM) - One of three basic methods (see also Amplitude and Frequency Modulation) of adding information to a sine wave signal in which its phase is varied to impose information on it.
Phase Shift - A change in the phase relationship between two alternating quantities.
Photodetector - Used on the receiving end of a fiber optic cable to convert light energy into electrical energy.
Physical Layer - Layer one of the seven layer ISO Reference Model for Open Systems Interconnection. The physical layer is responsible for the transmission of signals, such as electrical signals, optical signals, or radio signals, between computing machines.
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. Workspaces 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.
Poke-Thru - Penetrations through the fire-resistive floor structure to permit the installation of horizontal telecommunications cables.
Polymer - A substance made of repeating chemical units or molecules. The term is often used in place of plastic, rubber, or elastomer.
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.
POTS - Plain Old Telephone System
Power Level - The difference between the total power delivered to a circuit, cable, or device and the power delivered by that device to a load.
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.
Private Branch Exchange (PBX) - A private telephone switching system, usually located on a customer's premises connecting a common group of lines from one or more central offices to provide service to a number of individual phones.
Propagation Delay - Time required for a signal to pass from the input to the output of a device.
Protector - A device that limits damaging voltages on metallic conductors.
Protocol - A set of agree-upon rules and message formats for exchanging information among devices on a network.
PSELFEXT - Power Sum Equal Level Far End Crosstalk
PSNEXT - Power Sum Near End Crosstalk
Public Data Network - A network established and operated for the specific purpose of Providing data transmission services to the public.
Public Switched Network - Any common carrier network that provides circuit switching between public users, such as the public telephone network.
Pull Strength, Pull Tension - The pulling force that can be applied to a cable without affecting the specified characteristics of the cable.
Pulse - A current or voltage which changes abruptly from one value to another and back to the original value in a finite length of time.
Pulse Code Modulation (PCM) - The most common method of representing an analog signal, such as speech, by sampling at a regular rate and converting each sample to an equivalent digital code.
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Quadrature Amplitude Modulation (QAM) – A means of encoding digital data that uses variations in signal amplitude and phase. QAM signals have 2 2n states, where each state encodes 2N bits. The encodings most commonly used include QAM-4, QAM-16, QAM-64 and QAM-256.
Qualified – indicates compliance or accordance with specific standards or requirements.
Quarter-wave Antenna – A radio antenna that is one-fourth the size of the wavelength of the design frequency.
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R - Symbol for Resistance
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).
Rack Unit (RU) - A unit of measure of vertical space in an equipment rack. One rack unit is equal to 45 mm (1.75 inches).
Radio Frequency (RF) - The frequencies in the electromagnetic spectrum that are used for radio communications.
RCDD - Registered Communication Distribution Designer - A certification of BICSI, an industry organization, for individuals qualified to consult and design telecommunications distribution systems.
Reactance - A measure of the combined effects of capacitance and inductance on an alternating current. The amount of such opposition varies with the frequency of the current. The reactance of a capacitor decreases with an increase in frequency. The opposite occurs with an inductance.
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.
Resistance - In dc circuits, the opposition a material offers to current flow, measured in ohms. In ac circuits, resistance is the real component of impedance and may be higher than the value measured at dc.
Resonance - An ac circuit condition in which inductive and capacitive interact to cause a minimum or maximum circuit impedance.
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)
Ring - 1. A polarity designation of one wire of a pair indicating that the wire is that of the secondary color of a 5-pair group (e.g. the blue white wire of the blue pair). 2. A wiring contact to which the ring wire is attached. 3. The negative wiring polarity (see Tip).
Ring Network - A network topology in which terminals are connected in a point-to-point serial fashion in an unbroken circular configuration. Many logical rings are wired as a star for greater reliability.
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 standards documents, though most people continue to use the RJ-45 name for all 8-pin connectors.
RMS - Root Mean Square.
Rx – Receive
RZ - Return to Zero
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SAS, Single Attachment Station - Term used with FDDI networks to denote a station that attaches to only one of two rings in a dual ring environment.
SC Connector - A fiber optic connector having a 2.5mm ferrule, push-pull latching mechanism, and the ability to be snapped together to form duplex and multifiber connectors. SC connectors are the preferred fiber optic cable for premises cabling, and are recommended by the TIA/EIA-568-A Standard for structured cabling. Used with Ethernet 100Base-FX and 1000Base-LX/SX fiber optic media systems.
Scalability – The ability of a network to grow without degradation of quality.
Scanner - A cable testing device which uses TDR methods to detect cable transmission anomalies and error conditions.
Screen - see Shield
Segment - On Ethernet a media segment may be made up of one or more cable sections joined together to produce a continuous cable for carrying Ethernet signals.
Separator - Pertaining to wire and cable, a layer of insulating material such as textile, paper, Mylar, etc. which is placed between a conductor and its dielectric, between a cable jacket and the components it covers, or between various components of a multiple conductor cable. It can be utilized to improve stripping qualities, flexibility, or can offer additional mechanical or electrical protection to the components it separates.
Sheath - see Jacket
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".
Signal - The information conveyed through a communication system.
Signal-to-noise-ratio (S/N) - 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 - 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.
Sinusoidal - A signal which varies over time in proportion to the sine of an angle. Ordinary alternating current is sinusoidal.
Skew Rays - A ray that does not intersect the fiber axis. Generally, a light ray that enters the fiber at a very high angle.
Skin Effect - The tendency of alternating current to travel on the surface of a conductor as the frequency increases.
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.
Spectral Bandwidth - The difference between wavelengths at which the radiant intensity of illumination is half its peak intensity.
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.
ST Connector - Designation for the "straight tip" connector developed by AT&T. This fiber optic connector features a physically contacting non-rotating 2.5mm ferrule design and bayonet connector-to-adapter mating. Used with Ethernet 10Base-FL and FIORL links.
Star Network - A network in which all stations are connected through a single point.
Star Topology - A topology in which each outlet/connector is wired directly to the distribution device.
Static Charge - An electrical charge that is bound to an object. An unmoving electrical charge.
Station - A unique, addressable device on a network.
Step Index Fiber - An optical fiber in which the core is of uniform refractive index with a sharp decrease in the index of refraction at the core-cladding interface. Step index multimode fibers generally have lower bandwidths than graded index multimode fibers.
Step Insulated - Process of applying insulation in two layers. Typically used in shielded networking cables such that the outer layer of insulation can be removed and remaining conductor and insulation can be terminated in a RJ-45 type connector.
Strength Member - That part of a fiber optic cable that increases the cable's tensile strength and serves as a load bearing component. Usually made of Kevlar aramid yarn, fiberglass filaments, or steel strands.
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.
Synchronous - Transmission in which the data character and bits are transmitted at a fixed rate with the transmitter and receiver being synchronized.
Synchronous Digital Hierarchy (SDH) - International standard for optical digital transmission at hierarchical rates from 155 Mbps to 2.5 Gbps and beyond.
Synchronous Optical Network (SONET) - A USA standard for optical digital transmission at hierarchical rates from 155 Mbps to 2.5 Gbps and beyond.
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T1 - T1 is a 1.544 Mbps multichannel digital transmission system for voice or data provided by long distance carriers. Also referred to as DS1 (Data Services).
T3 - T3 is a 44.736 Mbps multichannel digital transmission system for voice or data provided by long distance carriers. Also referred to as DS3 (Data Services).
TC - Telecommunications Cross Connect.
Teflon - Dupont Company trademark for flourocarbon resins (see FEP and TFE).
Telecommunications Closet - see Closet
Telecommunications Equipment Room - see Equipment Room
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.
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 and pressure. Examples are polyvinyl chloride and polyethylene.
Through Penetration - A continuous opening that passes through both surfaces of a fire-rated barrier.
TIA - Telecommunications Industry Association - Body which authored the TIA/EIA 568-A "Commercial Building Telecommunications Wiring Standard" in conjunction with EIA.
Time Division Multiplexing (TDM) - A technique for combining many signals on a single circuit by interleaving bits or bytes of data from successive channels.
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.
Tip - 1. A polarity designation of one wire of a pair indicating that the wire is that of the primary (common) color of a 5-pair group (e.g. the white-blue wire of the blue pair). 2. A wiring contact to which the tip wire is connected. 3. The positive wiring polarity (also see "ring").
TNC - A threaded connector used to terminate coaxial cables. TNC is an acronym for threaded Neill-Concelman.
Topology - The physical or logical interconnection pattern of a network.
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.
Transducer - A device for converting mechanical energy into electrical energy.
Transfer Impedance - For a specified cable length, transfer impedance relates to a current on one 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 and egress of interfering signals. Shields with lower transfer impedance are more effective than shields with higher transfer impedance.
Transition Point (TP) - A location in the horizontal cabling where flat undercarpet cable connects to round cable.
Transmission Line - An arrangement of two or more conductors or a wave guide used to transfer a signal from one location to another.
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.
Transition Point - A location in the horizontal cabling where flat undercarpet cable connects to round cable.
TSB - Telecommunications Systems Bulletin
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.
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.
Tx - Transmit
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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.
Unshielded Twisted Pair (UTP) - Twisted pair cabling that includes no shielding. UTP most often refers to the 100 ohm Category 3, 5e, & 6 cables specified in the TIA/EIA 568-A standard.
USOC - Universal Service Order Code. Pronounced "U-Sock". An old Bell System term used to identify a particular service or device offered under tariff. Often used to refer to an old cable color code scheme that was current when USOC codes were in use.
Utility Pole - A customer-owned outside plant pole owned by a private or municipal utility.
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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.
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.
Virtual Circuit (VC) – a communications path through an internetwork that appears to be a dedicated circuit between two network devices.
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.
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W - Symbol for Watt or Wattage
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.
Wave Form - A graphical representation of the amplitude of a signal over time.
Wavelength - The distance between successive peaks or nodes of a wave.
Wavelength Division Multiplexing (WDM) - The process of combining and splitting signals on the basis of difference in their wavelengths.
WAN - Wide Area Network - A network connecting computers within very large areas, such as states, countries, and the world.
Wire fault - An error condition caused by a break in the wires or a short between the wires (or shield) in a segment of cable.
Wire Map - Pin to pin termination and continuity of each individual conductor. The wire map indicates continuity to the remote end, shorts between two or more conductors reversed pairs, split pairs, transposed pairs, and any other miswiring.
Wiring Closet - see Closet
Work Area - That area of the premises cabling where users are located. The area from the communications outlet to the equipment connected to the premises cabling. Loosely, an office, cubicle, and so forth.
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
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X - 1. Symbol for reactance. 2. Symbol for cross-connect.stored on the network.
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Z - Symbol for impedance.
Zone of Protection - The area in close proximity to and within a building’s lightning protection system. Several factors may make this area relatively immune to direct lightning strikes.
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