FAQs - Glossary of Terms

frequently asked questions

µm
See Micron (µm).

10BASE-FL
An implementation of the Institute of Electrical and Electronic Engineers (IEEE) Ethernet standard on 62.5/125-µm fiber optic cable, a baseband medium of 10 Mbps.

10BASE-T
An implementation of the Institute of Electrical and Electronic Engineers (IEEE) Ethernet standard on 24-AWG, unshielded, twisted-pair wiring, a baseband medium of 10 Mbps.

10BASE2
An implementation of the Institute of Electrical and Electronic Engineers (IEEE) Ethernet standard on thin coaxial cable, a baseband medium of 10 Mbps. The maximum segment length is just under 200m (656ft).

10BASE5
An implementation of the Institute of Electrical and Electronic Engineers (IEEE) Ethernet standard on twinaxial cable, a baseband medium of 10 Mbps. The maximum segment length is 500m (1,640ft).

100BASE-T
Official project name for 100 Mb/s Fast Ethernet.

100BASE-T4
100 Mb/s Fast Ethernet using 4-pair Category 3 cable.

100BASE-TX
100 Mb/s Fast Ethernet using 2-pair Category 5 cable.

100VG-ANY LAN
100 Mb/s LAN using Demand Priority Protocol originally developed by Hewlett Packard and AT&T for Category 3 cable.

1000BASE-T
A specification for Gigabit Ethernet over copper wire (IEEE Standard 802.3ab). The standard defines 1 Gb/s data transfer over distances of up to 100 meters using four pairs of Category 5e balanced copper cabling and a 5-level coding scheme.

1000BASE-TX
A specification for Gigabit Ethernet over copper wire (TIA/EIA). The standard defines 1 Gb/s data transfer over distances of up to 100 meters using four pairs of Category 6 balanced copper cabling.

1000Base-LX
A specification for Gigabit Ethernet over Fiber Optic cable (IEEE Standard 802.3z) at 1300nm wavelength.

1000Base-SX
A specification for Gigabit Ethernet over Fiber Optic cable (IEEE Standard 802.3z) at 850nm wavelength.

10 Gigabit Ethernet
The IEEE has initiated work on the specification of 10 Gigabit Ethernet over optical fiber cabling. The standard is planned for completion in 2001 or early 2002, with specifications for multimode and singlemode fiber.

802.3
Defined by the Institute of Electrical and Electronic Engineers (IEEE), these standards govern the use of the Carrier Sense Multiple Access/Collision Detection (CSMA/CD) network access method used by Ethernet networks

802.5
Defined by the Institute of Electrical and Electronics Engineers (IEEE), these standards govern the use of the token ring network access method.

802.11
Defined by the Institute of Electrical and Electronics Engineers (IEEE), these standards govern the use of wireless LANs.

A
See Ampere (A).

Adapter
A device that (1) enables different sizes or types of plugs to mate with one another or to fit into an information outlet, (2) provides for the rearrangement of leads, (3) allows large cables with numerous wires to fan out into smaller groups of wires, or (4) makes interconnections between cables.

Ad Hoc Cabling
Cabling scheme where different types of cabling components from different vendors are linked together to form a cabling system.

Administration Point
A location at which communications circuits are administered; that is, rearranged or rerouted by means of cross connections, interconnection, or information outlets.

Administration Subsystem
The part of a premises distribution system that includes the distribution hardware components where you can add or rearrange circuits. These components include cross connects, interconnects, information outlets, and their associated patch cords and plugs. Also called "administration points." See also Cross Connect and Information Outlets (IO).

American National Standards Institute (ANSI)
Organization responsible for the definition and maintenance of the Fiber Distributed Data Interface (FDDI) standard. ANSI is the principal group in the United States for defining standards. ANSI represents the U.S. in the International Standards Organization (ISO).

American Wire Gauge (AWG)
The standard gauge for measuring the diameter of copper, aluminum, and other conductors.

Ampere (A)
A standard unit of current. One ampere of current is produced by one coulomb of charge passing a point in one second.

Analogue Signal
A signal that represents information in a continuously variable and directly measurable physical quantity, such as voltage. Shaped like a wave, analogue signals, such as those transmitted over a telephone channel, vary in both frequency and amplitude proportionate to the voice or other signals initiating them. See also Digital Signal.

Analogue Transmission
A method of signal transmission in which the shape of the signal is a continuously variable and directly measurable physical quantity such as voltage.

ANSI
See American National Standards Institute (ANSI)

Application
A system, with its associated transmission method which is supported by telecommunications cabling.

Application Layer
The uppermost layer (layer 7) of the open systems interconnection (OSI) model. This layer is concerned with support to the user application and is responsible for managing the communication between applications, e.g. Email, File transfer, etc.

ASCII
The American Standard Code for Information Interchange. A widely-used 7 or 8-bit binary code used to represent alphabetic and numeric characters in computer understandable form.

Asynchronous
Two or more signals sourced from independent clocks, therefore having different frequency and phase relations.

Asynchronous Data Transfer
A method of data transfer in which each alphabetic or numeric character (represented by 7 or 8 bits) is preceded by 'start' and 'stop' bits to delineate the 7/8 bit pattern from the ideal pattern which otherwise occupies the (digital) transmission medium.

Asynchronous Transfer Mode (ATM)
A high speed cell-based switching and multiplexing technology based on segmentation of voice, data and video into fixed packets (cells). These cells are transferred along switched paths and are not received on a regular basis (hence the term asynchronous).

Asynchronous Transmission
A data transmission technique controlled by start and stop bits at each end of a character and characterized by an undetermined time interval between characters.

ATM
See Asynchronous Transfer Mode.

Attenuation
The effect of signal reduction, experienced with accumulating line length or distance of radio transmission.

AWG
See American Wire Gauge (AWG).

Backbone/Riser Closet
See Riser Telecommunications Closet.

Backbone/Riser Subsystem
See Riser Backbone Subsystem.

Backbone(s)
The part of a premises distribution system that includes a main cable route and facilities for supporting the cable from the equipment room to the upper floors, or along the same floor to the wiring closets.

Balanced Circuit
A circuit where equal and opposite signals are generated and sent on to two conductors. The better the balance of a circuit, the lesser is its emissions and the greater is its noise immunity (hence the better is its EMC performance).

Balanced Twisted Pair Cable
A cable consisting of one or more metallic symmetrical cable elements (twisted pairs or quads).

Balun
A device for matching impedance between a balanced to unbalanced line, usually twisted-pair and coaxial cable.

Bandwidth
The range of frequencies that can be used for transmitting information on a channel. It indicates the transmission-carrying capacity of a channel. Thus, the larger the bandwidth, the greater the amount of information that can pass through the circuit. Measured in Hertz or bit/s or MHz.km (for fiber).

Baseband
A network in which the entire bandwidth of the transmission medium is used as a single digital signal. Unlike broadband, no modulation techniques are used.

Basic Rate Interface (BRI)
The simplest form of network access available on the ISDN (integrated services digital network). The BRI comprises 2B + D channels for carriage of signaling and user information.

Bend Radius
The radius of curvature that fiber or copper can bend without breaking or causing excessive loss.

Bit Error Rate (BER)
A measure of quality of a digital transmission line, either quoted as a percentage, or more usually as a ratio, typically 1 error in 10E8 or 10E9 bits carried. The lower the number or errors, the better quality the line.

BNC Connector
The connector type used on many types of coaxial data communication equipment.

Bonding
The connecting together of all building and equipment electrical grounds to eliminate differences in electrical ground potentials.

BRI
See Basic Rate Interface (BRI).

Bridge(s)
A device used to link two subnetworks using the same communications method and sometimes the same kind of transmission medium.

Broadband
A network in which the bandwidth can be shared by multiple simultaneous signals that are encoded with radio frequency modulations.

Building Backbone Cable
A cable that connects the building distributor to a floor distributor. Building backbone cables may also connect floor distributors in the same building.

Building Distributor
A distributor in which the building backbone cable(s) terminate(s) and at which connections to the campus backbone cable(s) may be made.

Building Entrance Facility
A facility that provides all necessary mechanical and electrical services, that complies with all relevant regulations, for the entry of telecommunications cables into a building.

BUS
Consists of a common transmission path with a number of nodes attached to it. Sometimes referred to as linear network topology.

Bus Topology
A local area network (LAN) topology in which endpoints connect to a single wire or fiber, or set of wires or fibers, at any point. The Ethernet LAN is one example.

Cable Fill
The ratio of cable installed into a conduit/trunking against the theoretical maximum capacity of the conduit/trunking.

Cable Rack
The vertical or horizontal supports, usually made of aluminum or steel, that are attached to a ceiling or wall. Cables are laid in and fastened to the rack. Sometimes called trays.

Cable Routing Diagram
A detailed drawing showing the layout of the cable routes.

Cabling
A system of telecommunications cables, cords and connecting hardware that can support the connection of information technology equipment.

CAD/CAM
Computer-Aided Design/Computer-Aided manufacturing.

Campus
A premises containing more than one building adjacent or near to one another.

Campus Backbone Cable
The communications cable that is part of the Campus Backbone Subsystem and runs between building. There are four methods of installing campus backbone cable: in-conduit (in underground conduit), direct-buried (in trenches), aerial (on poles), and in-tunnel (in stream tunnels).

A cable that connects the campus distributor to the building backbone distributor(s). Campus backbone cables may also connect building cabling distributors directly.

Campus Cable Entrance
The point at which Campus Backbone Subsystem cabling (aerial, direct-buried, or underground) enters a building.

Capacitance
The property in a system of conductors and dielectrics that permits the storage of electrically separated charges whenever a difference in potential exists between the conductors. Capacitance is undesirable in copper wire cable because it interferes with signals traveling on the wire by opposing the desired flow of current.

Carrier Sense Multiple
Network access method using contention similar to Carrier Sense Multiple.

Access with Collision Avoidance (CSMA/CA)
Access/Collision Detection (CSMA/CD) used by LocalTalk networks. Unlike CSMA/CD, in this method the sending node requests permission to send from communications. It defines protocols for user or applications programs.

Carrier Sense Multiple Access/Collision Detection (CSMA/CD)
Network access method in which nodes contend for the right to send data. If two or more nodes attempt to transmit at the same time, they abort their transmission until a random time period of microseconds has transpired and then attempt to resend.

Category 3
For cable and connecting hardware products with transmission characteristics specified to 16 MHz, typically used to support digital transmission of 10 Mb/s.

Category 5
For cable and connecting hardware products with transmission characteristics specified to 100 MHz, typically used to support digital transmission of 100 Mb/s and above.

Category 5e
This is an enhanced version of Category 5, with additional parameters specified to enable parallel transmission with full duplex across the four pairs. Enhanced Category 5 specifications for cable and connecting hardware products with transmission characteristics specified to 100 MHz, intended to support digital transmission of 1000 Mb/s.

Category 6
For cable and connecting hardware products with transmission characteristics specified to 250 MHz, used to support digital transmission of 1 Gbp/s and above.

Category 7
For cable and connecting hardware products with transmission characteristics specified to 600 MHz. Category 7 is a cable standard only and will require a new connector standard to fully exploit transmission at the above frequencies.

Ceiling Distribution
Distribution system that uses the space between the false or suspended ceiling and the structural ceiling for housing horizontal cable routes.

Cell Relay
A fast packet switching technique which uses fixed-length cells. Generic name for ATM, SMDS and BISDN.

CENELEC
European committee for electrotechnical standardization.

CENELEC EN 50173
The European standard for generic cabling for customer premises.

CENELEC EN 50174
A proposed European cabling systems planning & installation standard developed by CENELEC.

Central Processing Unit (CPU)
A personal computer's (PC's) primary microprocessor chip.

Channel
The end to end transmission path connecting any two pieces of application-specific equipment. Equipment cables and work area cables are included in the channel.

Characteristic Impedance
A frequency-dependent resistance that quantifies the complex opposition to current flow offered by a transmission line.

Chromatic Dispersion
Chromatic dispersion describes the tendency for different wavelengths to travel at different speeds in a fiber. If operated at wavelengths where chromatic dispersion is high, optical pulses tend to temporally broaden, leading to intersymbol interference, which can produce an unacceptable bit error rate

Churn
The relocation of an individual or a group of individuals within a building such that the workspace or services to the workspace require change.

Circuit
A two-way communications path between electronic devices.

Cladding
The low refractive index material that surrounds the core of an optical fiber, usually pure silica.

Client
A node that requests network services from a server.

Client-Server
A technique by which processing can be distributed between nodes requesting information (clients) and those maintaining data (servers).

Closet
SYSTIMAX® SCS location for hardware, conduits, power panels, and electronics, such as multiplexers and concentrators.

Coating
A protective layer of material over the cladding of an optical fiber.

Coaxial Cable (Coax)
A cable with a center conductor surrounded by a thick insulation, surrounded by an outer conductor made of metal braid. An outer jacket insulation is optional.

Collapsed Backbone
This architecture is a backbone topology where wiring concentrators located at floor levels are attached in a star configuration to a central high performance switching concentrator.

Composite Cable
A cable construction technique that combines multiple cables or media in a single overjacket.

Conductor
A medium such as copper wire that can carry electrical current.

Conduit
A pipe, usually metal, that runs underground from floor to floor, or along a floor or ceiling to protect cables. In the Riser backbone Subsystem when riser telecommunications closets are not aligned, conduit is used to protect cable and provide the means for pulling cable from floor to floor. In the Horizontal Subsystem, conduit may be used between a telecommunications closet and an information outlet in an office or other room. Conduit is also used for in-conduit campus distribution, where it is run underground between buildings and intermediate manholes and is made of plastic encased in concrete. Multiduct, clay-tile conduit may also be used.

Connecting Block
A flame-retardant plastic block containing metal wiring terminal (quick clips) that establishes an electrically tight connection between the cable and the cross-connect wire.

Connecting Hardware
See Cross Connect.

Connector
A device that allows you physically to connect and disconnect copper wires or fibers in cable to equipment or to other wires or fibers. Copper wire and fiber optic connectors must often join transmission media to equipment or cross connects.

Consolidation Point
An interconnection point in horizontal cabling, typically used to support the re-arrangement of furniture cloisters.

Core
The central transmission area of a fiber. The core always has a refractive index higher than that of the cladding.

Cords
A short length of copper wire or fiber optic cable with connectors on each end. Used to connect equipment to cabling, or to connect cabling segments (cross-connection).

Coulomb (C)
A quantity of electricity transferred by a current of one ampere in one second.

CPU
See Central Processing Unit (CPU)

CRC
See Cyclic Redundancy Check (CRC).

Cross Connect
SYSTIMAX® SCS component where communication circuits are administered (that is, added or rearranged using jumper wire or patch cords). In 110 Connector Systems, Hook-Up Wire or patch cords are used to make circuit connections. In fiber optic connector systems, fiber optic patch cords are used. The cross connect is located in an equipment room or telecommunications closet. See also Jumper Wire and Patch Cord.

Cross-Connect Field
Copper wire or fiber terminations grouped to provide cross-connect capability. The groups are identified by color-coded sections of back boards mounted on the wall in equipment rooms or telecommunications closets, or by designation strips or labels placed on the wiring block or unit. The color coding identifies the type of circuit that terminates at the field.

Crosstalk
An electromagnetic coupling between two physically isolated circuits in a system. This coupling causes a signal on one circuit to induce a noise voltage on adjacent circuits, thereby causing signal interference.

CSA
Canadian Standards Association.

CSMA/CA
See Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

CSMA/CD
See Carrier Sense Multiple Access/Collision Detection (CSMA/CD)

Customer Premises Equipment (CPE)
Customer owned equipment used to terminate or process information from the public network e.g. Multiplexed or PABX.

Cut-Down
A method of securing a wire to a wiring terminal. The insulated wire is placed in the terminal groove and pushed down with a special tool. As the wire is seated, the terminal cuts through the insulation to make an electrical connection, and the spring-loaded blade of the tool trims the wire flush with the terminal. Also called punch-down.

Cyclic Redundancy Check (CRC)
A coded sequence of information allowing error checking and correction.

Data Communications Equipment (DCE)
General terminology for data communications equipment such as modems. A device that terminates a data communications session and provides encoding or conversion if necessary. See also Data Terminating Equipment (DTE).

Data terminating equipment (DTE)
The term used to describe any type of computer or other equipment, when connected to a data communications network.

Data Link Layer
Layer 2 of the Open Systems Interconnect (OSI) model; it defines protocols governing data packetizing and transmission into and out of each node.

dB
See Decibel (dB)

dB/km
See Decibel/kilometer (dB/km).

DB9
A standardized connector with nine pins for token ring and serial connections.

DB15
A standardized connector with 15 pins for Ethernet transceivers.

DB25
A standardized connector with 25 pins for parallel or serial connections.

DCE
See Data Communications Equipment (DCE).

Decibel (dB)
A unit used to measure relative increase or decrease in power, voltage or current, using a logarithmic scale.

Decibel/kilometer (dB/km)
A unit of measurement for fiber optic attenuation.

Delay Skew
Delay Skew is the difference in propagation delay between any two pairs within the same cable sheath.

Dielectric
A nonconducting or insulating material that resists passage of electric current.

Dielectric Cable
A nonconducting cable, such as fiber optic cable, without metallic members.

Dielectric Constant
The ratio of the capacitance of the insulated wire to that of the same wire uninsulated in air.

Dielectric Strength
A measure of the maximum voltage that the insulation of a particular cable can withstand without breakdown.

Digital Signal
A signal that represents information by a series of fixed, encoded, rectangular pulses, usually consisting of two possible voltage levels. Each voltage level indicates one of tow possible values or logic states, such as on or off, open or closed, true or false. See also Analogue Signal.

Digital transmission
A technique in which all information is converted into binary digits for transmission.

Dispersion
The tendency of a beam of light to spread out and loose its focus.

Distributor
The term used for the functions of a collection of components (for example, patch panels, patch cords) used to connect cables.

DIW
See Network Communications Cable (NCC) and Twisted Pair

DTE
See Data Circuit-Terminating Equipment (DTE) and also Data Terminating Equipment (DTE).

Dual-Fiber Cable
A type of fiber optic cable that has two single-fiber cables enclosed in a jacket of extruded plastic.

Ducts
The main feeder channels in which communication cable is routed between buildings in a campus environment. See also Campus Backbone Cable.

EIA
See Electronic Industries Association (EIA)

EIA/TIA
North American Standards organization.

EIA/TIA 568B
North American commercial building telecommunications wiring standard.

EIA/TIA 569A
North American commercial building standard for telecommunications pathways and spaces. Its purpose is to standardize specific design and construction practices within and between buildings which are in support of telecommunications media and equipment.

EIA/TIA 606
North American administration standard for the telecommunications infrastructure of commercial buildings. Its purpose is to provide guidelines for a uniform administration scheme for the cabling infrastructure.

Electromagnetic Compatibility (EMC)
The ability of a system, equipment or device to operate satisfactorily in its environment without introducing unacceptable electromagnetic disturbance, or being affected by that environment.

Electromagnetic Flux
Electric and magnetic fields (commonly referred to as emissions) generated by equipment or system.

ELFEXT
See Equal Level Far End Crosstalk

EMC
See Electromagnetic Compatibility.

EMI
See Electromagnetic Interference.

EN 50173
The European standard for generic cabling for customer premises.

EN 50174
A proposed European cabling systems planning & installation standard developed by CENELEC.

Equal Level Far End Crosstalk (ELFEXT)
Is the same as FEXT, except that the coupled signal at the remote end is relative to the attenuated signal at the remote end on the pair the signal was applied to at the local end.

Equipment Cable
A cable connecting equipment to a distributor.

Equipment Room
The room in which voice and data common equipment (for example, a DEFINITY switch) is housed, protected, and maintained, and where circuit administration is done using the trunk and distribution cross connects.

Equipment Subsystem
The part of a premises distribution system that includes the cable and distribution components in an equipment room and that interconnects system-common equipment, other associated equipment, and cross connects.

Ethernet
The common name for the most widely used local area network (LAN), generally conforming to the Institute of Electrical and Electronic Engineers (IEEE) 802.3 Standard.

Far End Crosstalk (FEXT)
Refers to the undesired coupling of signals from the transmit pair onto the receive pair at the other (=far) end. FEXT isolation is also expressed in dB. For some applications this is an important parameter, for most applications however, the NEXT values are more important.

Farad (F)
The standard unit of capacitance.

Fast Ethernet
A 100 Mb/s LAN Based On CSMA/CD Protocol. See 100BASET.

Federal Communications Commission (FCC)
A board of five commissioners, appointed by the President, that regulates all electronic communications systems originating in the United States, including telephone systems.

FEXT
See Far End Crosstalk.

FDDI
See Fiber Distributed Data Interface.

Fiber
Any filament or fiber, made of dielectric materials, that guides light. See also Fiber Optics.

Fiber Channel
This is an ANSI standard describing point to point and switched point to point physical interface, transmission protocol, signaling protocol, services and command set mapping of a high performance serial link for uses between mainframe computers and computer peripherals.

Fiber Distributed Data Interface (FDDI)
An American National Standards Institute (ANSI) standard for a fiber-based token ring physical and data link protocol that operates at a 100-Mbps data transfer rate.

Fiber Optic
A fiber optic cable in which individual optical fibers are formed into a cable for primary use in side building.

Fiber Optics
The technique of conveying lights or images through glass or plastic fibers. Incoherent fiber optics will transmit light but not an image; coherent fiber optics will transmit both and should actually be called "aligned fiber optics" because the fibers are all the same length and are held in a constant spatial relationship.

Fiber Optic Building Cable (LGBC)
A fiber optic cable in which individual optical fibers are formed into a cable for primary use in side building.

Fiber Optic Cable
A transmission medium consisting of a core of glass or plastic surrounded by a protective cladding, strengthening material, and outer jacket. Signals are transmitted as light pulses, introduced into the fiber by a light transmitter (either a laser or light-emitting diode [LED]). Some of the advantages offered by fiber optic cable are low data loss, high-speed transmission, large bandwidth, small physical size, light weight, and freedom from electromagnetic interference and grounding problems.

Fiber Optic Connectors
Connectors designed to connect and disconnect either single or multiple optical fibers repeatedly. Fiber optic connectors are use to connect fiber cable to equipment and interconnect cables.

Fiber Optic Cross Connection
Fiber optic apparatus for terminating cable in couplings. Designed for high-density cross-connection fields, the apparatus can terminate up to 72 fibers on each shelf, with up to nine shelves in a bay frame. Single shelves can also be wall mounted. Cross connections are handled with fiber optic patch cords. See also Patch Cord.

Fiber Optic Cross-Connect (LGX) Distribution System
A component of fiber optic cross-connect hardware. This component accommodates 24-216 fiber terminations. Also referred to as an LGX or shelf or frame.

Fiber Optic Interconnect
An interconnection unit used for circuit administration and built from modular cabinets. It provides interconnection for individual optical fibers but, unlike the fiber optic cross-connect panel, it does not use patch cords or jumpers. The fiber optic interconnect provides some capability for routing and rerouting circuits, but is usually used where circuit rearrangements are infrequent.

Fiber Optic Interconnection Unit (LIU)
A component of fiber pitch cross-connect hardware. This component accommodates 12, 24 or 48-fiber terminations. Also referred to as an LIU.

Fiber Optic Splice
A fiber optic cable splice is used to join together 2 or 24 fiber optic cable ends, permanently.

Field
See Cross-Connect Field.

File Server
A computer that stores data centrally for network users and manages access to that data. File servers can be dedicated so that no processes other than network management can be executed while the network is available, or nondedicated so that standard user applications can be run while the network is available.

Fire Walls
Walls that go from structural floor to structural ceiling and, therefore, help prevent fire from spreading from one area to another.

Flood Wiring
The concept of wiring for future growth, by providing full coverage of information outlets.

Floor Distributor
The distributor used to connect between the horizontal cable and other cabling subsystems or equipment (see telecommunications closet).

Foil screened twisted pair cable (FTP)
A cable that use's a metallic Foil to surround the conductors in a Twisted Pair cable.

Frame
A metallic structure for hanging switch hardware.

Frequency
The number of cycles completed by a signal in one second: measured in Hertz (Hz).

FTP
See Foil Screened Twisting Pair Cable.

Full Duplex
In contrast to half-duplex devices, full duplex ones allow permanent, simultaneous two-way transmission of information, without interaction or interference of receive and transmit signals

Full Duplex Ethernet
Full Duplex Ethernet will allow nodes to transmit and receive data at the same time, bringing aggregate throughput to 20 Mb/s. The CSMA/CD protocol may have to be disabled for the full duplex mechanism to function.

Gauge
A measure of a conducting wire's physical size, usually referred to as AWG (American Wire Gauge). See also American Wire Gauge (AWG).

Generic Cabling
A structured telecommunications cabling system, capable of supporting a wide range of applications. Generic cabling can be installed without prior knowledge of the required applications. Application-specific hardware is not a part of generic cabling.

Graded-Index Fiber
An optical fiber with a refractive index that gets progressively lower away from the axis. This causes the light rays to be continually refocused by refraction in the core. It bends the rays inwards and allows them to travel faster in the lower index of refraction regions. This type of fiber provides high bandwidth capabilities.

Ground
A conducting connection, intentional or accidental, between a circuit or equipment and the earth.

H
See Henry.

Henry (H)
The standard unit of inductance. The inductance of a current is a one Henry when a current variation of one ampere per second induces one volt.

Hertz (Hz)
The standard unit of frequency; equal to one cycle per second.

Half Duplex
A telecommunications device allowing two-way transmission of signals or other information, but only in one direction at a time. Thus a half-duplex device cannot simultaneously transmit and receive, though interspersed bursts in each direction are possible.

Horizontal Cable
A cable connecting the floor distributor to the telecommunications outlet(s).

Horizontal Runs
The part of the premises distribution system installed on one floor that includes the cabling and distribution components connecting the riser backbone or equipment wiring to the information outlet.

See horizontal subsystem.

Horizontal Length (HL)
The cable distance from the information outlet to the blue field of the cross connect. In SYSTIMAX® SCS, this is referred to as the Horizontal Subsystem.

Horizontal Subsystem
The part of a premises distribution system installed on one floor that includes the cabling and distribution components connecting the Riser backbone Subsystem to the information outlet via cross-connect components of the Administration Subsystem.

Hub(S)
A concentrator or repeater in a star topology at which node connections meet.

Hybrid Cable
An assembly of two or more different types of cable units, cables or categories covered by an overall sheath. It may be covered by an overall shield.

Hz
See Hertz (Hz).

ICEA
See Insulated Cable Engineers Association (ICEA).

IBM
International Business Machines Corporation.

IEC 60332
The international standard covering fire performance of cables.

IEEE
Institute of Electrical and Electronic Engineers in the USA. This organization is also involved in producing Local Area Network standards such as 10Base-T and Token Ring. such as Ethernet.

Individual Pair Screened
Where each twisted pair in one overall cable has its own screen.

InfiniBand Architecture
A high bandwidth switched network topology currently being developed for Storage Area Networks (SANS).

Insulation
A material having high resistance to the flow of electric current. Thin conducting wires are covered with color-coded insulation for protection.

Insulation Displacement
The type of wire terminals that require no wire stripping; when the wire is correctly attached, its insulation is displaced (pierced) to form a connection.

Insulation Resistance
The measure of the ability of an insulation material to resist the flow of current through it; usually measured in Megohm-feet (Mµ-ft).

Integrated Services Digital Network (ISDN)
Integrated voice and data network based on digital communications technology and standards interfaces.

Intelligent Buildings
Buildings that maximize the efficiency of its occupants and allow effective management of resources with minimum life-time costs (Source: European Intelligent Building Group).

Intercloset Cables
Cables that connect telecommunications closets.

Interconnect
A circuit administration point, other than a cross connect or information outlet, that provides capability for routing and rerouting circuits. It does not use patch cords or jumpers. Typically it is a jack-and-plug device used in smaller distribution arrangements or to connect circuits in large cables to those in smaller cables.

Interface Cards
See Network Interface Cards.

Interference
A signal impairment caused by the interaction of another unwanted signal.

International Standards Organization (ISO)
The organization responsible for the Open Systems Interconnect (OSI) standards. International Standards Organization.

International Telegraphy and Telephone Consultative Committee (CCITT)
A standards organization that, among numerous other activities, specializes in the electrical and functional characteristics of switching equipment. The CCITT sets standards for interfaces to ensure compatibility between data communications equipment (DCE) and date terminating equipment (DTE).

Interoperability
The ability to operate and exchange information in a heterogeneous network.

IO
See Information Outlets (IO).

ISO
See International Standards Organization (ISO). International Standards Organization.

ISO Seven Layer Model
A 7 layer hierarchical reference structure developed by the ISO for defining, specifying and relating communications protocol.

ISO/IEC IS 11801
An international standard for generic cabling for customer premises.

ISO/IEC 14763-1
The international standard for basic administration of generic cabling.

Isochronous Ethernet
This is part of the IEEE 802.9 integrated services LAN standard. It is an extension of 10Base-T which provides for the inclusion of a 6.144 Mbps isochronous (real time and delay sensitive) data service in addition to the 10 Mb/s 10BaseT packet service. It will provide multimedia capability.

ISDN
See Integrated Services Digital Network (ISDN).

J
See Joule (J).

Jack
A receptacle used with a plug to make electrical contact between communications circuits. Jacks and their associated plugs are used in a variety of connecting hardware applications including adapter, information outlets, and equipment connections.

Jacket
The flexible covering of a cable, used to protect the color-coded conductors inside.

Joule (J)
A unit of work or energy equal to 0.7375 foot-pounds.

Jumper
A cable unit or cable element without connectors used to make a connection on a cross-connect.

Jumper Wire
A short length of Connectorized copper wire used to route a circuit by linking two cross-connect termination points.

Keying
A mechanical feature of a connector system which guarantees correct orientation of a connection or prevents the connection to a jack or optical fiber adapter of the same type intended for another purpose.

LAN
See Local Area Network (LAN)

Lays
The twists in twisted-pair cable. Two single wires are twisted together to form a pair; by varying the length of the twists, or lays, the potential for signal interference between pairs is reduced.

LC Connector
A high density connector for fiber optic applications used in both public and private networks. This high performance connector is available in both singlemode and multimode.

LIGHTPACK Cable
A cable core design that allows bundles of optical fibers in a cable core without central strength members.

Link
The transmission path between any two interfaces of generic cabling. It excludes equipment cables and work area cables.

Link Budget
Optical loss budget that determines the maximum distance allowable between station. Loss and dispersion factors are included.

LIU
See Fiber Optic Interconnection Unit (LIU).

Local Area Network (LAN)
A data communications network consisting of host computers or other equipment interconnected to terminal devices, such as personal computers, often via twisted-pair or coaxial cables. LAN's allow users to share information and computer resources. Typically, a network is limited to a single premises.

Multimedia
A means of conveying information with components in different media such as voice, music, text, graphics, image and video.

Multimode
Many light rays (modes) propagating through the fiber core.

Multimode fiber
Optical fibers that have a large core and that permit nonaxial rays or modes to propagate through the core. 62.5 micron is the common standard core size for premises cabling systems.

Nanometer (nn)
A unit of length in the metric system denoting one-billionth of a meter (10µm).

National Electrical Code (NEC)
A nationally recognized safety standard for the design, construction, and maintenance of electrical circuits. The NEC, sponsored by the National Fire protection Association (NFPA), generally covers electrical power wiring within buildings.

NCC
See Network Communications Cable (NCC).

Near End Crosstalk (NEXT)
Refers to the undesired coupling of signals from the transmit pair onto the receive pair on the same (=near) end. NEXT isolation is expressed in dB and is a measure of how well the pairs in a cable are isolated from each other.

NEC
See National Electrical Code (NEC).

Network
The local and long-distance telecommunications capability provided by common carriers for switch and private line telecommunications services. A system of software and hardware connected in a manner to support data transmission.

Network Architecture
Network topology and design.

Network Communications Cable (NCC)
Network Communications Cable, often called NCC, is generally used in the Riser Backbone Subsystem in locations not involving plenums. The cable consists of 24-AWG, annealed-copper conductors insulted with color-coded polyvinyl chloride (PVC) in twisted pairs, encased in an outer PVC jacket whose frictional properties permit it to be pulled in conduit without the aid of lubricants. This type of cabling used to be referred to as Direct Inside Wire (DIW).

Network Interface
The point of interconnection between building communications wiring and outside communications lines (telephone company facilities.).

Network Interface Cards (NICs)
The piece of equipment that is installed into the expansion port of a personal computer and allows communication between the PC and the network.

Network Layer
The network layer is layer 3 of the OSI model. This layer sets up an end-to-end connection across a network determining which permutation of individual links to be used. Thus the network layer performs overall routing functions.

NEXT
See Near-end cross talk.

nm
See Nanometer (nm).

Node(S)
A piece of communications equipment on the network.

Noise
The term used for spurious signals produced in a conductor by sources other than the transmitter to which it is connected. Noise can affect a legitimate signal to the extent that it is inaccurate or indecipherable when it reaches the receiver. The higher the speed of data transmission, the worse the effects of noise become.

Numerical Aperture
The size of the vertex angle of the largest core of rays that can enter or leave a multimode fiber optic system, multiplied by the refractive index of the medium in which the vertex of the core is located.

Ohm (W)
The standard unit of electrical resistance. One volt will cause one ampere of current to flow through on ohm of resistance.

Open system interconnection (OSI)
A conceptual model specified by CCITT recommendations in the X200 series. The model describes the 7-layer process of communication between 'co-operating' computers. The model provides a standard for the development of communication protocols allowing for computers of different manufacturers to be interconnected.

Optical Connectors
See Fiber Optic Connectors.

Optical Cross Connection
See Fiber Optic Cross Connection.

Optical Fiber
A transmission medium consisting of a core of glass or plastic surrounded by a protective cladding. Signals are transmitted as light pulses, introduced into the fiber by a light transmitter i.e. Laser or an LED.

Optical Interconnect
See Fiber Optic Interconnect.

Optical Splice
See Fiber Optic Splice.

Optical Time-Domain Reflectometer (OTDR)
An instrument that characterizes cable loss by measuring the backscatter and reflecting of injected light as a function of time. It is useful for estimating attenuation and for locating splices, connections, and breaks.

OSI
See Open Systems Interconnect (OSI).

OTDR
See Optical Time-Domain Reflectometer (OTDR).

Outlets
A term used to describe the sockets provided in the work location of a Structured Cabling System. These are usually 8-pin modular sockets which can support a variety of services e.g. voice, video and data.

PABX PABX
Private Automatic Branch Exchange. A private switching system that switches calls both internally within a building or premises and outside to the telephone network.

Packet-Switching
A type of exchange or network which conveys a string of information from origin to destination by cutting it up into a number of packets and carrying each independently. A packet-switched effect could be achieved by sending individual pages of a book through the post separately. The receiving device reassembles the message. Thus a direct connection between origin and destination does not exist at any point.

Pair
Two wires grouped (usually twisted) together and marked with reciprocal color coding. See also Twisted Pair.

Patch Cord(s)
A short length of copper wire or fiber optic cable with connectors on each end used to join communications circuits as a cross connect.

Patch Panel(s)
A cross-connect designed to accommodate the use of patch cords. It facilitates administration for moves and changes.

Pathway(s)
Designated cable routes and/or support structures in a false floor or ceiling.

PBX
See Private Branch Exchange (PBX)

PDS
See Premises Distribution System (PDS).

Peripheral(s)
Additions to a system, a resource e.g. printer, scanner, etc.

Permanent link
The transmission path between two mated interfaces of generic cabling, excluding equipment cables, work area cables and cross-connections.

pF
See Picofarad (pF)

PHY
Physical layer of the Fiber Distributed Date Interface (FDDI) standard. Also used to refer to the actual hardware used to implement the physical layer (PHY entity).

Physical Layer
Layer 1 of the open systems interconnection (OSI) model. The physical layer protocol is the hardware and software in the line terminating device which converts the databits needed by the datalink layer into the electrical pulses, modem tones, optical signals or other means which will transmit the data.

Physical Topology
Physical cabling layout i.e. ring, bus, star wired etc.

Picofarad (pF)
A unit of capacitance used to designate capacitance unbalance between pairs of capacitance unbalance of the two wires of a pair to ground. One picofarad equals one trillionth of a farad.

Pin
A conductor on a plug or connector.

Plenum Cable
Cable specifically designed for used in a plenum, the space above a suspended ceiling use to circulate air back to the heating or cooling system in a building. Plenum cable has insulated conductors often jacketed with TEFLON or HALAR on copper and low smoke PVC on fiber optics to give them low flame-producing and low smoke-producing properties.

Plug
A device used for connecting wires to a jack. It is typically used on one or both ends of equipment cords or on wiring for interconnects or cross connects.

PMD
Physical Medium Dependent part of the Fiber Distributed Data Interface (FDDI) standard. Determines the specifications for the fiber optic transmitters and receivers, fiber optic cable, fiber optic connectors, and fiber optic bypass switch.

Polyvinyl Chloride (PVC)
A flame-retardant thermoplastic insulation material that is commonly used in jacks or building cables. Both plenum are riser.

Port
The cable terminations in the equipment system at which various types of communications devices, switching equipment, and other devices are connected to the transmission network.

Ports
A computer interface capable of transmitting and or receiving information.

Power Sum
A method of testing and measuring crosstalk in multi-pair cables that accounts for the sum of crosstalk affecting a pair when all other pairs are active. This is the only method of specifying crosstalk performance that is suited to cables with more than four pairs.

Premises Distribution System (PDS)
The transmission network inside a building or group of buildings that connects various types of voice and data communication devices, switching equipment, and information management system together, as well as to outside communications networks. It includes the cabling and distribution hardware components and facilities between the point where building wiring connects to the outside network lines, back to the voice and data terminals in to office or other work locations. The system consists of all the transmissions media and electronics, administration points, connectors, adapters, plugs, and support hardware between the building's side of the network interface and the terminal equipment required to make the system operational.

Presentation Layer
Layer 6 of the OSI model. Responsible for identifying the syntax of the data being transmitted.

PRI
See Primary Rate Interface (PRI)

Primary Rate Interface (PRI)
ISDN standard interface comprising 23 B + 1 D channel for North America, and 30 B + 1 D Channel for Europe. See Basic Rate Interface (BRI) and Integrated Services Digital Network (ISDN).

The North American 1.544 Mb/s T1 (23B+D) or European 2.048 interface (PRI) Mb/s E1 (30B+D) ISDN interface typically used to connect ISDN PBXs to the public ISDN.

Private Branch Exchange (PBX)
A private switching system usually serving an organization, such as a business or government agency, and located on the customer's premises. It switches calls both inside a building or premises and outside to the telephone network, and can sometimes also provide access to a computer from a data terminal.

Propagation Delay
A signal traveling from end to end of a simplex link is delayed in time by an amount equal to the length of cable divided by the velocity of propagation for that transmission medium. This delay is called Propagation Delay.

Proprietary Networks
Networks that are not designed, installed to any standard based guidelines and do not relate specifically to any relevant standard.

Proprietary Systems
Systems that are not Standards specific and therefore inoperable with standards based equipment.

Protocol(s)
A rule of procedure by which computer devices intercommunicate. Thus a protocol is the equivalent of a human language, with punctuation and grammatical rules.

Public Network Interface
A point of demarcation between public and private network. In many cases the public network interface is the point of connection between the network provider's facilities and the customer premises cabling.

Pulling Tension
The amount of pull, measured in pounds, placed on a cable during installation.

Punch-Down
See Cut-Down.

PVC
See Polyvinyl Chloride (PVC).

Quad Fiber Cable
A type of fiber optic cable that has four single cables enclosed in an extruded jacket of polyvinyl chloride (PVC), with a rip cord for pulling back the jacket to access the fibers.

Raceway
Any distribution method designed for holding cables, e.g. conduit, metal or plastic trunking, cable trays, etc.

Rack
A vertical or horizontal open support, usually made of aluminum or steel, that is attached to a ceiling or wall. Cables are laid in and fastened to the rack.

Redundancy Risers
A fail-safe method of splitting and routing riser/ backbone cables via two or more riser cores. Also known as diverse routing.

Resistance
The property of a conductor that determines the current produced by a given potential difference. It impedes the flow of current and results in the dissipation of power as heat. Resistance is measured in ohms.

Return Loss
The Channel Return Loss (RL) is a measure of the consistency of the impedance down the length of not just the cable, but also the connections and the patch cables.

Ribbon Fiber Cable
A cable that accommodates 1 to 12 ribbons, each ribbon having 12 fibers for a cable size range of 12 to 216 fibers. Ribbon cables are designed for use in large distribution systems where small cable size and high pulling strength are important.

Ribbon Riser Cable
An optical fiber, nonconductive, riser (OFNR)-rated premises cable containing optical fibers in ribbons.

Ring
A closed loop network topology.

Ring In (RI)
Port for connecting multistation access units (MAUs) together.

Ring Out (RO)
Port for connecting multistation access units (MAUs) together.

Riser(s)
The term used to describe a space utilized by backbone cabling to house communications cabling and other building services. This space should preferably be specified, or allowed for, at the time of the building design.

Riser Backbone Subsystem
The part of a premises distribution system that includes a main cable route and structure for supporting the cable from an equipment room (often in the building basement) to the upper floors, or along the same floor, where it is terminated on a cross connect in a riser telecommunications closet, at the network interface, or at distribution components of the Campus Backbone Subsystem. The Riser Backbone Subsystem usually extends from an equipment room (often in a building's basement) to the upper floors in a multistory building, or along the same floor in a low-wide building. It is terminated on a cross connect in a riser telecommunications closet, at the network interface, or on the distribution components of the Campus Backbone Subsystem.

RO
See Ring Out (RO)

Router(s)
A router can be used to connect networks with similar protocols (802.5 token ring local area networks [LANs]) or dissimilar Open Systems Interconnection (OSI) model protocols (802.5 token ring LANs and X.25 packet-switching networks). Routers are more sophisticated than bridges and can be used to prevent some of the speed mismatch, security, and reliability problems that occur in large networks.

An intermediate system between two or more networks capable of forwarding data packets at the network layer (layer 3).

Satellite Cabinet
Surface-mounted or flush-type wall cabinets for housing circuit administration hardware. Satellite cabinets, like satellite telecommunications closets, supplement riser telecommunications closets by providing additional facilities for connecting horizontal cables from information outlets in user work areas. Sometimes referred to as a "satellite location".

Satellite Telecommunications Closet
A walk-in or shallow wall closet that supplements a riser telecommunications closet by providing additional facilities for connecting riser backbone cables to horizontal cables from information outlets. Also referred to as a "satellite location." See also Riser Telecommunications Closet.

Scaleable
The ability to adapt to different bit rates.

Screened Cable
See Foil Screened Twisted Pair Cable.

Serial Communications
See Serial Data Transmission.

Serial Data Transmission
Data transmission between computer devices using only a single circuit path. Whole bytes of information (8 bits) are sent in sequential pattern. Compares with parallel transmission. Parallel transmission is often used internally within computing devices because of the higher processing speeds which are possible, but for long-distance telecommunication, serial transmission is more economic in terms of line plant.

Serial Port(S)/Transmission
Normally a DB 9 pin connector located on the mother board of a PC. A technique in which each Bit of information is sent sequentially on a single channel.

Server(S)
Host Computer(s).

Session Layer
Layer 5 of the OSI model. Responsible for establishment and control of dialogues between users on different machines. Synchronization for reliable data transfer and token management to control use of the connection are services provided by this layer.

Service Entrance
See Campus Cable Entrance.

Serving Closet
See Satellite Telecommunications Closet

Sheath
A common term for the collection of twisted pairs of multipair cables.

Shield
The metallic layer that surrounds insulated conductors in shielded cable. The shield may be the metallic sheath of the cable or the metallic layer inside a nonmetallic sheath.

Shielded Twisted Pair Cable (STP)
An electrically conducting cable comprising one or more elements each of which is individually shielded. There may be an overall shield in which case the cable is referred to as a shielded twisted pair cable with an overall shield.

Signal To Noise Ratio (SNR)
The ratio of the signal magnitude to the noise magnitude and is usually expressed in dB. The higher the SNR of a system, the better is its performance.

Simplex
A transmission means allowing only one direction of transmission. (For example public broadcast radio).

Single-Fiber Cable
A plastic-coated fiber surrounded by an extruded layer of plastic encased in a synthetic strengthening material, and enclosed in a plastic sheath.

Singlemode
Optical fiber with a small core diameter in which only single mode is capable of propagation. 8.3 micron is the common standard core size.

Sleeves
Short lengths of rigid metal pipe, approximately 4 in. (10.1 cm) in diameter, located in riser telecommunications closet, that allows cables to pass from floor to floor when closets are vertically aligned. Sleeves also provide for easy pulling of cable.

Slots
Openings in the floor of riser telecommunications closets that allow cables to pass thorough from floor to floor when closets are vertically aligned. A slot accommodates more cables than an individual sleeve.

SNR
See Signal to Noise Ratio.

Sonet
Synchronous Optical Network; provides broadband connectivity for existing networks on a global scale.

Source Routing
A bridge uses source routing when the route to be followed is carried within each frame by the source stations. The source station acquires and maintains information by a search process, allowing parallel bridges to exist and to share traffic between the same two rings.

vSplice
The physical joining of two or more copper wires or optical fibers to form a common connection.

Star
A physical point to point network topology.

Star Physical Topology
See Star.

Star Quad
A cable element which comprises four insulated conductors twisted together. Two diametrically facing conductors from a transmission pair.

Star Topology
See Star.

ST Connector
See Straight-Tip (ST) Connector.

Storage Area Network (SAN)
A high speed network or subnetwork of shared storage devices.

Straight-Tip (ST) Connector
A fiber optic connector used to join single fibers together at interconnects or to connect them to fiber optic cross connects.

Stranded Cable
A strong woven-copper-wire cable used to support cable in aerial distribution systems. The cable is lashed to the stranded cable during installation.

STP
See Shielded Twisted Pair Cable.

Structured Cabling
Flexible cabling scheme which allows rapid reconfiguration for office moves through patching.

Stud Cable
A short cable (usually 25 ft [7.6 m] or less) that extends from a cable terminal, protector, or block and is used to make connections to such devices.

Support Hardware
The racks, clamps, cabinets, brackets, trays, tools, and other equipment that provide the physical means to attach the transmission media and connecting hardware to walls or ceilings.

Surge
SurgeA sudden voltage rise and fall in a electrical circuit.

Switching
A function carried out by a switching hub, alleviating traffic by making virtual connections between transmitting and receiving nodes.

System-Common Equipment
The equipment on a premises that provides functions common to terminal devices such as telephones, data terminals, integrated workstations terminals, and personal computers. Typically, the system-common equipment is the private branch exchange (PBX) switch, data packet switch, or central host computer. Often called common equipment.

Synchronization
The method by which the bit patterns appearing on digital line systems may be properly 'clocked' and interpreted - allowing the beginning of particular patterns and frame formats to be correctly identified.

Synchronous
Signals that are sourced from the same timing reference and hence are identical in frequency.

Synchronous Data Transfer
Data transfer employing a strictly regular pattern, rather than using start and stop bits to distinguish character patterns from idle line operation.

SYSTIMAX SCS
Brand name of Avaya's Structured Cabling System.

TCP/IP
TCP/IP See Transport Control Protocol/Internet Protocol (TCP/IP).

Telecommunications
A branch of technology concerned with the transmission, emission and reception of signs, signals, writing, images and sounds; that is, information of any nature by cable, radio, optical or other electromagnetic systems.

Telecommunications Closet
A room where cables are terminated on cross-connect fields, where circuit administration takes place. There are two kinds of telecommunications closets: riser telecommunications closets and satellite telecommunications closets. See also Riser Telecommunications Closet and Satellite Telecommunications Closet.

An enclosed space for housing telecommunications equipment, cable terminations, and cross-connect cabling. The telecommunications closet is a recognized cross-connect point between the backbone and horizontal cabling subsystems.

Telecommunications Outlet
A socket where the horizontal cable terminates. The telecommunications outlet provides the interface to the work area cabling.

Terminal Block
A protected or unprotected unit of wiring blocks, connecting blocks, and troughs that serves as a transition point between cable conductors.

Thermoplastic
A plastic material that softens and flows when heated and becomes firm when cooled. This process can be repeated.

Thick Coax
The transmission medium used for Ethernet or IEEE 802.3 10Base5 LANs. It is a 50 ohm thick coax cable (commonly referred to as the thick yellow cable).

Thin Coax
The transmission medium used for IEEE 802.3 10Base2 LANs (sometimes referred to as CheaperNet). It is a 50 ohm thin coax cable.

Thermoset
A plastic material that is crosslinked by a heating process known as curing. Once cured, thermosets cannot be reshaped.

TIA/EIA
North American Standards Organization.

TIA/EIA 568A or B
North American Commercial Building Telecommunications Wiring Standard.

TIA/EIA 569
North American commercial building standard for telecommunications pathways and spaces. Its purpose is to standardize specific design and construction practices within and between buildings which are in support of telecommunications media and equipment.

TIA/EIA 606
North American administration standard for the telecommunications infrastructure of commercial buildings. Its purpose is to provide guidelines for a uniform administration scheme for the cabling infrastructure.

TP-PMD
Twisted Pair Physical Medium Dependent. A twisted pair version of the FDDI standard that allows 100Mb/s transmission over Category 5 copper cable.

Token
A special data sequence that is continuously sent around the ring. The term "token" represents permission to transmit from one station to its downstream neighbor.

Token Ring
A data link protocol type which implements media access control (MAC) by the circulation of a token around a complete ring network. Each station in the ring sequentially receives the opportunity to send data on the network as the token is passed around the network.

Token Ring LAN
A 4 or 16 Mb/s LAN standard based on token passing access protocol originally developed by IBM. Sometimes referred to as IEEE 802.5 or ISO 8802-5 standard.

Topology
The physical or electrical configuration of a local communications network (that is, the shape or arrangement of the system). The most common distribution system topologies are the bus, ring, and star.

TP-PMD
Twisted Pair Physical Medium Dependent. A twisted pair version of the FDDI standard that allows 100 Mb/s transmission over Category 5 copper cable.

Transducer
A sensing device that converts a signal from one form to another e.g. mechanical to electrical.

Transmission Distance
The actual length of the path from the transmitter of one node to the receiver of the next downstream node. The maximum transmission distance is determined by the maximum signal loss (attenuation limit) that can be withstood between any transmitter and receiver.

Transmission Media
The various types of copper wire and fiber optic cable used for transmitting voice, data, or video signals.

Transport Control Protocol/Internet Protocol (TCP/IP)
A common network layer and transport layer data networking protocol.

Transition Point
A location in the horizontal cabling where a change of cable form takes place.

Transport Layer
Layer 4 of the OSI model. The transport layer provides for end-to-end data relaying service across any type of data network and is responsible for end-to-end reliability.

Trunk
A communication link between two switching systems. The term switching typically includes equipment in a central office (or the telephone company) and PBXs. A tie trunk connects PBXs. Central office trunks connect a PBX to the switching system at the central office. See also Private Branch Exchange (PBX)

Twinaxial Cable (TWINAX)
Two insulated conductors inside a common insulator, covered by a metallic shield and enclosed in a cable sheath.

Twisted Pair(s)
Two insulated copper wires twisted together. The twists, or lays, are varied in length to reduce the potential for signal interference between pairs. In cables greater than 25 pairs, the twisted pairs are grouped and bound together in a common sheath. Twisted pair is the most common type of transmission media.

UL
See Underwriters Laboratories (UL)

Underwriters Laboratories (UL)
A private testing laboratory concerned with electrical and fire hazards of equipment. With SYSTIMAX® SCS components, several abbreviations are used to designate the approved use.

Unshielded Twisted Pair Cable
Normal copper building cable, capable of high-speed data transmission. Techniques exist to address the signal impairments due to the transmission characteristics of copper media and to limit the radiated emission of UTP media.

UTP
See Unshielded Twisted pair (UTP)

Video Conferencing
Real time communications via video between two or more users at separate locations.

Volt (V)
The standard unit of electromotive force or electrical pressure. One volt is the amount of pressure that will cause one ampere of current to flow through one ohm of resistance.

W
See Watt (W)

WAN
See Wide Area Network (WAN)

Watt (W)
A unit of power equal to one joule per second.

Wavelength
The physical distance of one electromagnetic wave cycle.

Wide Area Network (WAN)
Any physical network technology that spans large geographic distances. WANs usually operate at slower speeds and have higher delays than local area networks (LANs).

Windows
Graphics based operating system developed by Microsoft.

Wiring Block
A molded plastic block that is designed in various pair configurations to terminate cable pairs and establish pair location on 110 Connector Systems.

Wiring Closet
See Telecommunication Closet.

Wireless LANs
Local area network that communicates using radio technology.

Work Area
A building space where the occupants interact with telecommunications terminal equipment. A user's work area which is typically 9 sq. meter or 100 sq. ft.

Work Area Cable
A cable connecting the telecommunications outlet to the terminal equipment.

Work Area Subsystem
The part of a distribution system that includes the equipment and extension cords from the information outlet to the terminal device.

X.25
A communication architecture developed by the International Telegraph and Telephone Consultative Committee (CCITT).

Zone Method
A ceiling distribution method in which ceiling space is divided into sections or zones. Cable is then run to the center of each zone to serve the information outlets nearby.