Glossary of Technical Terms (F-K)

(We wish to thank Unicom for their contributions.)

# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z



Fast Ethernet* – A version of Ethernet which operates at 100 Mbps. See 100Base-Tx and 100Base-FX.


FDDI (Fiber Distributed Data Interface)* – A high-speed networking standard. The underlying medium is fiber optics and the topology is a dual-attached, counter-rotating Token Ring. The FDDI protocol has also been adapted to run over traditional copper wires.


Fiber Channel* – A form of high-speed fiber optic transmission designed primarily for communications between mainframe computers, and between mainframe computers and high-speed peripherals such as disk drives. Sometimes used for general-purpose networking.


Fiber Optic Cable* – A type of cable consisting of glass or plastic fibers that are used to carry light signals. Fiber optic cable supports transmission speeds up into the 100Mbps.


Fiber Optic Transmission* – A communications scheme whereby electrical data is converted to light energy and transmitted through optical fibers.


Flame Resistance – The ability of a material not to propagate flame once the heat source is removed


Flex Life – The measurement of the ability of a conductor to withstand repeated bending.


FOIRL (Fiber Optic Inter Repeater Link)* – A fiber optic signaling method based on the IEEE 802.3 standard governing fiber optics. Allows up to 1,000 meters (3,280 ft.) of multi-mode duplex fiber optic cable in a point-to-point link.


Frame Relay* – An ITU standard for the interface to a public frame-switching network designed to provide high-speed frame transmission with minimum delay across the wide area. It operates at layer two, and is used in public and private networks, gradually replacing X.25 and leased-line networks.


Full-Duplex* – A communications method in which a transmission path is provided in each direction, so that each end can simultaneously transmit and receive.


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Gauge – A term used to denote the physical size of a wire.


Gbps* – Billions of bits per second.


Giga – A numerical prefix denoting one billion (109).


Gigabit Ethernet* – A variant of Ethernet which operates over multi-mode fiber optic cable, single mode fiber optic cable, or unshielded twisted pair, at 1,000 Mbps.


Ground – A conducting connection between an electrical circuit and the earth or other large conducting body to serve as an earth thus making complete electrical circuit.


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Half-Duplex* – A communications method in which one end transmits while the other receives, then the process is reversed. This was common in wide area point-to-multipoint circuits, such as those used in many SNA networks.Head End -A central point in a broadband network that receives signals on one set of frequency bands and retransmits them on another set of frequencies. The head end is viewed as a central hub. Every transmission on a broadband network must go through the head end.


Hard Drawn Copper Wire – Copper wire that has not been annealed after drawing.


Head End* – A central point in a broadband network that receives signals on one set of frequency bands and retransmits them on another set of frequencies. The head end is viewed as a central hub. Every transmission on a broadband network must go through the head end.


Hi-Pot – A test designed to determine the highest voltage that can be applied to a conductor without breaking through the insulation.


Horizontal Cabling* – That portion of a building’s cabling system which extends from the wiring closets to the individual workstations, servers, telephones, and other devices. This is generally copper twisted pair cable.


Hot Swapping* – The process of replacing a module without bringing down the system. This process occurs by sliding an active module into or out of a fully powered unit without shutdown.


Hub* – The center of a star topology network or cabling system. Typically used in older Ethernet and token ring networks. A device connected to a hub receives all the transmissions of all other devices connected to that hub. Hubs are now being replaced in many cases by LAN switches.


Hybrid cable* – An assembly of two or more cables, of the same or different types or categories, covered by one overall sheath.


Hybrid Network* – A LAN consisting of a number of topologies and access methods. For example, a network that includes both token ring and Ethernet.


HZ (Hertz)* – A measure of frequency or bandwidth.


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IDC (Insulation Displacement Contact)* – A type of wire terminating connection in which the insulating jacket is cut by the connector when the wire is inserted.


IEEE (Institute of Electrical and Electronic Engineers)* – A standards-making body responsible for implementing many standards used in LANs, including the 802.x series.


IEEE 802.1D* – See “Spanning Tree”.


IEEE 802.1p* – An IEEE standard for prioritizing time-critical flows and filtering multicast traffic to contain traffic in layer-two networks. The 802.1 p header includes three bits for prioritization, allowing for eight priorities to be established.


IEEE 802.1Q* – An IEEE standard for providing a virtual LAN capability within a campus network, used in conjunction with IEEE LAN protocols such as Ethernet and token ring.


IEEE 802.2* – A data link standard outlining how basic data connectivity over cable should be set up. Used with the IEEE 802.3, 802.4 and 802.5 standards.


IEEE 802.3* – The IEEE’s specification for Ethernet, including both physical cabling and layer-two protocol.


IEEE 802.5* – The IEEE’s specification for token ring, including both physical cabling and layer-two protocol.


IEEE 802.10* – The IEEE’s protocol for providing security in a metropolitan area network. A variant of 802.10 has sometimes been used to provide a virtual LAN service within a campus network, although this is now generally replaced with 802.1 Q.


IEEE 802.11b* – Insertion Loss is the amount of the signal that is lost (attenuation) as the signal passes through a connection or interface.


Impedance – The total opposition that a circuit offers to the flow of alternating current or any other varying current at a particular frequency. It is a combination of resistance R and reactance X, measured in ohms.


Inductance – The property of a circuit or circuit element that opposes a change in current flow, thus causing current changes to lag behind voltage changes. It is measured in henrys.


Insulation – A material having high resistance to the flow of electric current. Often called a dielectric in radio frequency cable.


Insulation Resistance – The radio of the applied voltage to the total current between two electrodes in contact with a specific insulation, usually expressed in megohms-M feet.


Internetwork* – Two or more networks connected by bridges or routers.


Intranet* – The use of various Internet tools and protocols, especially HTTP and HTML, within an organization.


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Jacket – An outer nonmetallic protective covering applied over an insulated wire or cable


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Kbps* – Thousands of bits per second.


Ki I o (K) – A numerical prefix denoting 1000 (103).


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