An ATM term . Functional Group : A collection of functions related in such a way that they will be provided by a single logical component. Examples include the Route Server Functional Group (RSFG), the IASG (Internetwork Address Sub-Group), Coordination Functional Group (CFG), the Edge Device Functional Group (EDFG) and the ATM attached host Behavior Functional Group (AHFG).


Feature Group A. Characterized by a seven-digit local telephone number access code and line side termination to the customer at the first point of switching.


See Feature Group B.


See Feature Group C.


See Feature Group C and Equal Access.


See Feature Group D.


Feature Group D - Equal Access. See Feature Group D, also see Equal Access.


Frequency Hopping Spread Spectrum. A technique used in spread spectrum radio transmission systems, such as Wireless LANs and some PCS cellular systems. FHSS involves the conversion of a data stream into a stream of packets, each of which is prepended (prepend means added to the front of) by an ID contained in the packet header. Short bursts of packets then are transmitted over a range of 75 or more frequencies, with the transmitter and receiver hopping from one frequency to another in a carefully choreographed "hop sequence." FCC regulations specify that each transmission can dwell on a particular frequency no more than 400 milliseconds . A large number of other transmissions also may share the same range of frequencies at the same time, with each using a different hop sequence. The potential remains, however, for the overlapping of packets. The receiving device is able to distinguish each packet in a packet stream by reading the various IDs, treating competing signals as noise. In a wireless LAN environment, DSSS typically operates in the 2.4 GHz frequency band , which is one of the ISM (Industrial Scientific Medical) bands defined by the FCC for unlicensed use. Although most manufacturers prefer FHSS, Direct Sequence Spread Spectrum (DSSS) is used by some. See also CDMA, DSSS, ISM and Spread Spectrum.


The word "fiasco," meaning a failure, is derived from the ancient Italian art of glass blowing. If a Venetian glass blower made a mistake while creating a fine, delicate bottle , the imperfect vessel was turned into an ordinary drinking flask which, in Italian, is called a "fiasco." A fiasco is a disaster. My favorite use of the word comes from John Doer, superstar of the Silicon Valley venture capital powerhouse, Kleiner Perkins Caufield & Byers. Referring to the skill of picking startups , he said, "You're only as good as your last fiasco."


A shortened way of saying "fiber optic ." Fiber is made of very pure glass. In Bill Gates' book called "the Road Ahead," he says that optical fiber is so clear and pure that if you looked through a wall of it 70 miles thick, you'd be able to see a candle burning on the other side. Digital signals, in the form of modulated light, travel on strands of fiber for long distances. The big advantage that fiber has over copper is that it can carry far, far more information over much, much longer distances. The short history of fiber optics for communications is that scientists keep discovering more and more ways of putting more and more information down one single strand of fiber. Based on my own personal researches, no one has any idea what the eventual capacity limit of a strand of fiber optic might be. I have personally asked many scientists (including one Nobel Physics prize winner) and all seem to think there must be a theoretical limit. But they don't know what it is. And they believe we have many, many years of breakthroughs in fiber still to go. As of the time of this writing, SONET OC-192 (Synchronous Optical NETwork Optical Carrier Level 192) systems are being deployed fairly routinely by a number of major long distance carriers . Each OC-192 strand supports approximately 10 Gbps. With DWDM (Dense Wavelength Division Multiplexing), as many as 32 " windows ," or wavelengths of light, can be overlaid into a single strand at OC-192, yielding a total of approximately 320 Gbps. Fiber is the American spelling. The spelling in England, Europe, Canada, Australia and New Zealand is fibre. See also the following definitions beginning with fiber. See Optical Fiber for an essay on the advantages of fiber as a communications medium. See also Chromatic Dispersion, OC-192 and SONET.

Fiber Axis

In an optical fiber, the line connecting the centers of line circles that circumscribe the core , as defined under "tolerance field."

Fiber Bragg Grating

FBG. An FBG is a narrowband reflection filter permanently written into the core of single-mode optical fiber that enables the type of wavelength precision that is necessary for WDM systems to successfully combine, control, and route multiple "colors" of light within a single optical fiber. FBG act as fine optical filters separating and filtering multiple wavelengths of light propagating in the same fiber that can select a wavelength with a precision of plus or minus 0.02 nanometer. These gratings are typically used in signal monitoring and gain flattening applications.

Fiber Buffer

The material surrounding and immediately adjacent to an optical fiber that provides mechanical isolation and protection. Buffers are generally softer than jackets.

Fiber Bundle

An assembly of parallel unbuffered optical fibers, in intimate contact with one another and secured, usually with an epoxy or other adhesive . Each endface of the bundle is typically finished to a flat or other optical surface, usually at right angles to the axis of the bundle. Such bundles are used to transmit optical power or images. Bundles used to transmit images must maintain spatial coherence amongst the relative positions of the respective fibers at each end (aligned bundles). There is no requirement for this if the bundle is used to transmit optical power only. Fiber bundles were employed in early, short- distance communication applications, but have become obsolete in modern telecommunications.

Fiber Channel

There is no such thing as Fiber Channel. See Fibre Channel.

Fiber Control Office Terminal

FCOT is a generic term for a fiber terminal that can be configured for full digital, full analog or mixed communications.

Fiber Distributed Data Interface

FDDI. A set of ANSI/ISO standards that, when taken together, define a 100 million bits per second (Mbps), timed-token protocol, Local Area Network that uses fiber optic cable as the transmission medium. The standards define Physical Layer Medium Dependent, Physical Layer, Media Access Control, and Station Management entities. The standard specifies: multi-mode fiber, 50/125, 62.5/125, or 85/125 core-cladding specification; and LED or laser light source; and 2 kilometers for unrepeatered data transmission at 40 million bits per second (Mbps).

Fiber Exhaust

A fiber optic term. Fiber exhaust comprises the noxious light emissions from a fiber optic engine, the device which generates the light signals signals in an optical fiber transmission system. Much as an internal combustion engine creates noxious emissions, fiber optic engines (e.g., LEDs and Laser Diodes) create noxious light emissions, which can be extremely hazardous to your health. Actually, the preceding is a joke, like "frequency grease," which is used to overcome static noise in a radio system. Now for the truth: Fiber exhaust simply means that the capacity of a fiber optic transmission has been exhausted. The solution is 1) to lay more fiber, 2) to increase the speed of the system through an upgrade of light sources and detectors, or 3) to use WDM (Wavelength Division Multiplexing) or DWDM (Dense WDM) to increase capacity through the support of multiple wavelengths of light. See also Bucket o' Dial Tone, DWDM, Frequency Grease, SONET and WDM.

Fiber Grating

A fiber optics term. Fiber gratings are sections of optical fiber that have periodic changes in their refractive index "written" into the core with ultraviolet light. The fiber grating creates nearly arbitrary combinations of signal reflection and transmission spectra. Fiber gratings can be used as optical filters and taps. Fiber gratings also can be used as lasers (believe it or not) through the use of resonant cavities defined by highly- reflective regions in the grating. EDFAs (Erbium Doped Fiber Amplifiers ) use fiber grating to flatten the gain (i.e., power amplification level) across a range of wavelengths amplified, thereby reducing issues of crosstalk between closely- spaced wavelengths. EDFAs also use fiber grating to create filters that separate wavelengths and group them into bands, allowing certain wavelengths to be transmitted or reflected selectively. Fiber gratings are used in OADMs (Optical Add/Drop Multiplexers), in order to add and drop individual light wavelengths, which can be separated by as little as fractions of a nm (nanometer, or billionths of a meter). See also Diffraction Grating, EDFA, and OADM.

Fiber Identifier

A test instrument that can differentiate between live and dead fibers in a working cable and can identify a preselected fiber to which a special transmitter has been attached.

Fiber in the Loop


Fiber Loop Carrier

See FLC.

Fiber Loss

The attenuation (deterioration) of the light signal in optical fiber transmission.

Fiber Mile

Let's say that you have two sheaths of fiber, each of which contains ten fibers and runs for one mile. That is one route mile (total distance of all fibers), two sheath miles (two sheaths running one mile), and twenty fiber miles (20 fibers running one mile).

Fiber Optic

See Fiber and Fiber Optics.

Fiber Optic Amplifier

As light, like electricity or any other form of electromagnetic energy, travels through a physical medium, it attenuates, or loses intensity. At some point in a communications transmission system, you must take your increasingly weak signal and boost it back to its original strength. In analog systems, you simply amplify the weak incoming signal and send it on its way. In addition to amplifying the information signal, any accumulated noise is also amplified. In digital signals, you first regenerate the signal, then amplify it, then send it on its way, with no recognition of or regard for any noise present. Most fiber transmission systems accomplish this process by converting the original light signal on the fiber to electrical impulses, regenerate the signal, then amplify it, then convert it back to light pulses , then send it on its way. This takes significant energy and equipment ” not altogether convenient for an underwater cable of several thousand miles. With new fiber optic amplifiers you no longer need to convert the light signal to electrical impulses. A fiber optic amplifier uses special fiber doped with erbium to act as the amplifier. Light comes into this special fiber, is pumped with the correct frequency laser and is amplified with extremely high gain and very low noise through a process of chemical light amplification. It's truly amazing technology. See Erbium-Doped Fiber Amplifier for a more technical explanation.

Fiber Optic Attenuator

A small device with two connectors. It reduces the amount of light passing through it, similar to the way sunglasses reduce the amount of light entering your eyes so you can see better.

Fiber Optic Buffer

Plastic coating on individual fibers. There are 12 colors to distinguish them from each other.

Fiber Optic Cable

See Fiber.

Fiber Optic Connector

There are three types: SC, ST and FC. The FC connector can be considered an earlier vintage connector but it was pre-dated by the biconic and SMA. FC connectors were specifically designed for telecommunications applications and initially came into prominence overseas. It came into its own in the 1980s and was the earliest design to incorporate the now standard 2.5mm ceramic ferrule. It also provided non-optical disconnect performance. Another advantage was this connector offered tunable keying which allowed it to be adjusted in order to minimize loss. The FC connector incorporated a threaded coupling nut which provided a secure connection, however as with the biconic and SMA, it did not allow for quick connect and disconnect as the coupling nut had to be rotated many times to thread or unthread the connector. Technicians also found it difficult to work with the threaded connectors particularly if the technician had large hands. The ST connector can be considered as the first of the contemporary connector designs. It utilizes the 2.5mm ferrule which is available in ceramic, zirconia, stainless steel , or plastic materials and is produced as a singlemode or multimode version. A variety of physical contact ceramic and zirconia ferrule styles allow the ST to achieve optimal performance. It is also available as an epoxyless version. The ST connector is easily recognizable because of its quick release bayonet-style locking mechanism. Unlike the threaded connectors, the ST only requires a quarter turn to complete a mating or demating cycle. In the opinion of some people in the industry, one of the early drawbacks to the ST connector was that it was not designed to be pull proof which meant that it could optically disconnect when the patch- cord was pulled. The SC connector began to see widespread deployment in the early 1990's particularly among the RBOCs (Regional Bell Operating Companies) and several Independents. It is available in both singlemode and multimode designs. The SC is easily distinguishable by its square body style and utilizes a push - pull feature for mating and demating. The push - pull feature is preferred by many customers because when the fer- rules come into contact in the mating sleeve of the adapter there are no rotational forces which could potentially damage a fiber or score the ferrules. This feature also eliminates a potential buildup of particulate in the mating sleeve which could possibly degrade optical performance. The SC is also designed as a pull-proof connector. A pull-proof connector is designed so that the ferrule is decoupled from the connector housing to which the fiber cable is attached. Therefore the connector maintains optical contact when fiber cable is pulled outward or sideways , thus eliminating the possibility of a service outage . In a non- pull-proof connector such as the earlier ST's, the connection can be broken when cable is pulled with a force that is greater than the spring force, which is around 2 - 3 pounds . Since the SC mating and demating is accomplished by push - pull force rather than rotational force, it readily lends itself to duplex connection configurations because it requires less space to engage and disengage.

Fiber Optic Distribution Panel

A termination device and organizer. It houses splice trays where connector plugs (called pigtails) are attached to the ends of fiber- optic cables.

Fiber Optic Gyroscope

A coil of optical fiber that can detect rotation about its axis.

Fiber Optic Inter Repeater Link

An 802.3 Ethernet standard for connecting two repeater devices at 10 million bits per second.

Fiber Optic Link

A transmitter, receiver, and cable assembly that can transmit information between two points.

Fiber Optic Test Procedure


Fiber Optic Tracer

A device typically based on a flashlight used to test the continuity of optic fibers and to trace multimode fibers from proper connections.

Fiber Optic Transmission System

See Fiber Optics, SDH and SONET.

Fiber Optic Waveguide

A relatively long thin strand of transparent substance, usually glass, capable of conducting an electromagnetic wave of optical wavelength (visible region of the frequency spectrum) with some ability to confine longitudinally directed, or near-longitudinally directed, lightwaves to its interior by means of internal reflection.

Fiber Optics

A technology in which light is used to transport information from one point to another. More specifically, fiber optics are thin filaments of glass through which light beams are transmitted over long distances carrying enormous amounts of data. Modulating light on thin strands of glass produces major benefits in high bandwidth, relatively low cost, low power consumption, small space needs, total insensitivity to electromagnetic interference and great insensitivity to being bugged . All these benefits have great attraction to anyone who needs vast, clean transmission capacity, to the military and to anyone who runs a factory with lots of electronic machinery. The first field trial of an AT&T lightwave system took place in Chicago in 1977. There has been a rapid improvement in cost effectiveness of fiber systems, expressed as cost per bit per kilometer. A one hundredfold increase in cost performance in one five-year period ” from 1980 to 1985. Some versions of fiber optics now carry 40 Gbps (forth billion bits per second) in support of more than 600,000 uncompressed voice conversations, and that's over a single wavelength. Some systems run as many as 40 wavelengths through a technique known as Dense Wavelength Division Multiplexing (DWDM). See also DWDM and SONET.

Fiber Pair

Optical fiber transmission systems often, but not always, are deployed in pairs. First, you have to understand that light can only travel in one direction through a strand of fiber. It can go fast. But it can only travel in one direction. Now, let's consider the LAN (Local Area Network), where fiber is installed with a single fiber or a dual fiber. In the LAN, fiber often is deployed on the basis of a single fiber because it's cheaper. In a single fiber LAN, the devices (e.g., a switch or hub, and a server) transmit in half-duplex (i.e. one way at a time). Then they switch quickly to other direction. This is the way a typical local phone line works, i.e. the phone line from your telephone company's central office to the phone on your desk. A fiber communications system, like a LAN, may also be installed with two fibers, or fiber pairs, with the devices using one fiber to transmit and one to receive in full-duplex (i.e., simultaneous two-way) mode. While this approach requires twice the fiber and twice the port interfaces at the device level, the speed of transmission is improved by a factor of at least two. In a FDDI (Fiber Distributed Data Interface) LAN backbone network, each of two fibers continuously is active, with one transmitting in the clockwise direction and one in the counter-clockwise direction. This dual counter-rotating ring configuration is for purposes of redundancy and resiliency, as a break across both fibers at a single physical point will not isolate any two devices. In other words, any device can communicate with any other device on the FDDI network, in one direction or the other.

Now let's consider the WAN (Wide Area Network) domain. In the WAN, fiber typically is deployed in a pair configuration. In some implementations , one fiber is used to transmit and one to receive. In a SONET/SDH implementation, fiber networks are deployed in a dual counter-rotating ring configuration, much like that of FDDI networks, and for the same reasons of redundancy and resiliency. See also FDDI, Fiber Optic, and SONET.

Fiber Pigtail

A short length of optical fiber, permanently fixed to a component, used to couple power between the component and the transmission fiber.

Fiber Remote

Fiber Remote extends what Northern Telecom calls Intelligent Peripheral Equipment using dark single or multimode fiber cable. Fiber Remote operates over a range of typical campus distances ” from thousands of feet to several miles. Distance is site specific, determined by variables such as the type and quality of the fiber installed and the number of connectors and splices. The signal attenuation between the local PBX system and the remote IPE shelves should not exceed a 13 dB loss. Fiber Remote is used when users prefer a single switch; when users have a campus with right of way for running fiber where the distance between the local and remote site is within 6 miles; where there's limited riser space in a large high rise building; where a user needs to alleviate switch room congestion and where security is of utmost importance (e.g. in military bases).

Fiber Spudger

Shaped like a pencil, it's a gadget technicians use to move around and find their way through fiber optic cables on their hunt for one single fiber optic.

Fiber Swap

Winstar also was one of the first companies to engage in the type of fiber "swap" transactions that have become so controversial in 2001-2002 in the wake of Global Crossing Ltd.'s collapse. Starting in 1998, for instance, Winstar signed a series of contracts with Williams Communications Group Inc., in which Williams agreed to pay Winstar $400 million over four years for access to its portions of its telecom network. Winstar then turned around and agreed to pay Williams $644 million over seven years. This transaction gave both companies "profits" they could book and thus make their shares look more attractive to investors. Winstar eventually went broke.

Fiber Switch Cross-Connect

FXC. A type of Optical Cross-Connect (OXC). See OXC.

Fiber to the Cabinet

A network architecture in which an optical fiber connects the telephone switch to a streetside cabinet where the signal is converted to feed the subscriber over a twisted copper pair. See also Fiber to the Curb.

Fiber to the Curb

FTTC refers to the installation and use of optical fiber cable directly to the curbs near homes or any business environment as a replacement for "plain old telephone service" (POTS). Think of removing all the telephone lines you see in your neighborhood and replacing them with optical fiber lines. Such wiring would give us extremely high bandwidth and make possible movies-on-demand and online multimedia presentations arriving without noticeable delay. The term "fiber to the curb" recognizes that optical fiber is already used for most of the long-distance part of your telephone calls and Internet use. Unfortunately , the last part - installing fiber to the curb - is the most expensive. For this reason, fiber to the curb is proceeding very slowly. Meanwhile, other less costly alternatives, such as ADSL on regular phone lines and satellite delivery, are likely to arrive much sooner in most homes . Fiber to the curb implies that coaxial cable or another medium might carry the signals the very short distance between the curb and the user inside the home or business. "Fiber to the building" (FTTB) refers to installing optical fiber from the telephone company central office to a specific building such as a business or apartment house. "Fiber to the neighborhood" (FTTN) refers to installing it generally to all curbs or buildings in a neighborhood. Hybrid Fiber Coax (HFC) is an example of a distribution concept in which optical fiber is used as the backbone medium in a given environment and coaxial cable is used between the backbone and individual users (such as those in a small corporation or a college environment).


Slang expression to describe a customer who thinks he knows everything about cable. Usage: "That fiberoptichead wouldn't know a drop from a fish job."


A battery- powered device that connects to both ends of a fiber optic cable allowing people (typically craftspeople) to talk over the cable. The complete device (two ends) costs $1,000 to $2,000 and often comes with a headset.


In simultaneous media events in Washington and Montreal on October 12, 1989, Northern Telecom and Bell Northern Research (BNR) unveiled "FiberWorld," which they referred to "as a vision and commitment to deliver the world's first completely family of fiber-optic access, transport, and switching products."


The European, Australian, Canadian, British and New Zealand spelling. The American spelling is fiber. Whoops, except in the case of Fibre Channel, which is correct, even in American English. See Fiber, Fiber Optics and Fibre Channel.

Fibre Channel

Servers and networks are the mainstays of business. The dependence on data exchange between computers and between devices is pushing the limits of current computing architectures, which must evolve to support high-speed connections. To address this need, the American National Standards Institute (ANSI) developed several standards to define high-speed connections between devices that later became known as fibre (or fiber) channel. The potential in the fibre channel standard encouraged several major companies and organizations to back the movement, and in 1994 it was ratified as an official ANSI standard. Fibre channels are divided into five layers (listed below). Much like the Open Systems Interconnection (OSI) model, each layer defines a particular function of the system.

FC-0: Layer 0 defines the physical aspects of a fibre channel including the connection types, transmission media, signaling, and other optical and electrical parameters.

FC-1: Layer 1 outlines the encoding and decoding of information on a channel and error correction routines.

FC-2: Layer 2 is the meat of the fibre channel architecture in that it defines how to break down a data stream into frames and reassemble them again. This layer also negotiates flow control between devices, as well as other advanced aspects of transmitting and receiving data.

FC-3: Layer 3 allows access to advanced fibre channel functions, such as the ability to use multiple fibre channel ports working in parallel to act as a larger virtual connection and the ability to send a single transmission to multiple destinations.

FC-4: Layer 4 is the interface between the fibre channel hardware and the high level protocols that use the hardware to communicate. Because a fibre channel is a combination of the best of channel and networking architectures, it can handle protocols from both equally well and even allow them to work at the same time over the same interface.

Because of the structure of the architecture, fibre channels can operate at speeds from 133 Mbps to over 1,000 Mbps and can transmit and receive at the same time. In addition, high-level application interfaces like IPI, SCSI, IP, and ATM can operate flawlessly over the fibre channel architecture while using the same physical interfaces. The fibre channel topology is also flexible. It can be configured in a ring, point-to-point, or star topology. The adaptability and flexibility of a fibre channel make it ideal for storage area networks and network attached storage systems because it can provide a high-speed hardware connection between computers, servers, devices, and even displays and can be configured to drop into nearly any existing network configuration.

FC's speed of data transmission is due not only to the fundamental nature of the transmission system, but also to the fact that FC is a serial link technology. In other words, FC is an I/O (Input/Output) interface over which data is streamed in serial fashion across an established link. FC provides a channel connection for dedicated or switched point-to-point connection between devices. "Channel connections" are hardware-intensive, low in overhead, and high in speed; "network connections" typically are software- intensive , high in overhead, and therefore slower. The downside is that channel connections tend to be limited to a relatively small number of devices with pre-defined addresses. Actually, FC will support, through separate ports, both channel and network connections. It also will support not only its own protocol, but also higher level protocols such as FDDI, SCSI, HIPPI and IPI. The physical topology of Fibre Channel can be point-to-point, ring, or star. In a star configuration, the interconnecting switching device is known as a "Fabric," which can be a circuit switch (star), an active hub (star) or a loop (ring).

Fibre Channel supports the transfer of data in frames, with a payload of 2,048 bytes. A CRC (Cyclic Redundancy Check) mechanism is employed for purposes of detection and correction of transmission errors. Flow control is supported through switch buffers, in a Fabric implementation. Three service classes are supported. Class 1 provides the equivalent of a dedicated physical connection; it is the highest quality of service, and is most effective for very high-speed transfers of large amounts of data. Class 2 is a connectionless grade of service, making use of multiplexed frame switching, with multiple sources sharing the same channels; Class 2 supports confirmation of frame delivery. Class 3 is identical to Class 2, minus confirmation of frame delivery.

The applications for Fibre Channel initially were for high-speed data and image transfer in NAS (Network-Attached Storage) and SAN (Storage Area Network) applications. In the recent past, much attention has been focused on the real-time transfer of audio and video, as well. As a result, Fibre Channel is being implemented for video file transfer and video playback applications in post-production digital video and movie studios , and in the broadcast backbone. Competing standards include 10GbE and ESCON. See also 10GbE, CRC, ESCON, FDDI, HIPPI, IPI, and SCSI. www.FibreChannel.com

Fibre Channel ” Arbitrated Loop

FC-AL. A Fibre Channel application for Storage Area Networks (SANs), FC-AL supports high-speed access to storage arrays over loops as long as 10 kilometers over a single Fibre Channel link, non-amplified, and at data rates as high as 100 MBps (MegaBytes per second). In a dual loop architecture, data rates are doubled to as much as 200 MBps; rates of 400 MBps are anticipated in the near future. Logically, FC-AL operates as a full-duplex, point-to-point, serial data channel. As many as 126 hosts can be connected to a given storage device; intermediate and cascading FC-AL hubs and concentrators can serve to improve costs, although there are corresponding performance degradations. FC-AL earns the tag "arbitrated" by virtue of the fact that access to the storage system is arbitrated on the basis of level of privilege, with fractional bandwidth services supported. The next generation of FC-AL, designated FC-EL (Fibre Channel-Enhanced Loop) is under development at ANSI. See also Fibre Channel and SAN.

Fibre Channel ” Enhanced Loop

FC-EL. The next generation of FC-AL (Fibre Channel-Arbitrated Loop), FC-EL is under development at ANSI. See also FC-AL and Fibre Channel.

Fibre Channel Fabric

A fabric is one or more Fibre Channel switches in a single configuration. Fabric switches provide 100 MBps per port, so adding devices to a switch actually increases the aggregate bandwidth. Fabric switches also provide enhanced services to allow registration of devices and the discovery of targets (disks) by initiators (servers). Fabric switches may be connected together to form extended storage networks for large enterprises . The addressing scheme used for fabrics supports up to 15 1/2 million devices, making fabrics a very scalable architecture.

Fibre Channel GLM

GLM stands for Gigabit Linking Module, a generic Fibre Channel transceiver unit that integrates the key functions necessary for installation of a Fibre Channel media interface on most systems. They provide complete Fibre Channel FC- 0 functionality on easy to install daughter cards. A specification for this standardized universal module was developed in Fibre Channel's early days to help streamline the development process for various Fibre Channel products and their multiple versions. For example, optical and Copper GLMs can be swapped on many vendors ' Fibre Channel adapter cards. Included are transmit and receive optics, drivers, clock and data recovery, serializer, deserializer and laser safety features.

Fibre Channel Industry Association

Formed in January 1993, as the Fibre Channel Association, the FCA worked to encourage the utilization of Fibre Channel, complementing the standards development efforts of the ANSI T11 committee. The mission of the FCA is "to provide a support structure for system integrators, peripheral manufacturers, software developers, component manufacturers, communications companies and computer service providers." On August 18, 1999, the Fibre Channel Association (FCA) and the Fibre Channel Community (FCC), two organizations for the advancement of Fibre Channel technology and Storage Area Network solutions, merged into one association, the Fibre Channel Industry Association (FCIA). www.fibrechannel-europe.com.

Fibre Channel Node

Device connected to a Fibre Channel fabric, possibly a PC, disk drive, or RAID array, as well as an FC-AL.

Fibre Jack

Fibre jack is a small-form full-duplex (i.e. two fibres) fibre connecter developed by Panduit. It has been approved for publication as a standard under TIA/EIR-604.6 (FOCIS-6).


IBM's acronym for Fibre Connectivity, which is its implementation of the S/390 ESCON storage protocols over a Fibre Channel switch fabric.


Field Identifier. A USOC and ISDN SPID term. FID is widely used in the Telco business related to USOCs. The purpose of USOCs (Universal Service Ordering Codes) is to define a customer's service and equipment. FIDs (field identifiers) are used to describe more detailed and specific attributes of those USOCs. For example, the USOC for Remote Call Forwarding - RCD- will have a FID associated with it specifying the telephone number that calls will be forwarded to. See USOC.


Fidelity is the quality or state of being faithful. In the domain of electronic devices such as TV sets, radios, and record players (Lest I risk dating myself , systems that play tapes and CDs are lumped under my category of record players.), fidelity refers to the extent to which the device faithfully (i.e., accurately) reproduces the original audio or visual signal. Hi-Fi systems are noted for their high level of fidelity. In the domain of WLANs (Wireless Local Area Networks), Wi-Fi (Wireless Fidelity) refers to 802.11b wireless Ethernet. In the domain of marriage , fidelity refers to remaining faithful (i.e., not cheating on) your spouse. In the domain of the U.S. Marine Corps, "Semper Fidelis" translates from Latin as "Always Faithful" (to the Corps). See also 802.11.


An electronic bulletin board technology for transfer and receipt of messages. According to PC Magazine, the origins of FidoNet date back to the early 1980s, when the two authors of the BBS software Fido, who lived on opposite coasts, needed an easy way to exchange modifications they made to the source code. They designed a system where, as a nightly event, the board would shut down and run utilities that automatically transferred the changed files between the author's BBSs. The logical next step was to permit the exchange of private mail messages called NetMail, between the sysops. The author found these capabilities so useful that they include them as part of the Fido BBS (Bulletin Board Software) package. It didn't take long for an informal network of Fido nodes to come into existence, all running the Fido software and exchanging various utility and program files and NetMail among sysops. Like other BBSs, the FidoNet BBSs had their own SIGs, or Special Interest Groups, where users with similar interests could exchange messages in a way similar to what on-line services call conferences or forums. By 1986 a Fido sysop had extended the NetMail concept to allow SIGs to share public messages among the BBSs, and EchoMail was born. In the years since, BBS authors and FidoNet users and sysops extended these capabilities to other BBS packages, and FidoNet grew. It currently has over 11,000 nodes covering most of the world. Many of the existing public and private networks go through FidoNet gateways into the Internet Mail system, which carries e- mail over a group of interconnected networks to universities, government agencies, military branches, and corporations. FidoNet technology uses store-and-forward messaging and is based on point-to-point communications between nodes.


  1. One half (every other line) of a complete television picture "frame", consisting of every other analog scan line. There are 60 fields per second in American television.

  2. A place with no phones or other communications capability where an important person inevitably is when you need some vital information, service or device that only he or she can provide. "I'm sorry, the chief technician is in the field today, and can't be reached." Few "fields" are actually fields. They're usually downtown office buildings.

  3. The specific location of data within a record. In the jargon of database management systems, many fields make up one record Many records make up one file. A field is one of the basic subdivisions of a data record. The record on you in your company's database might include your name, your address, your salary, etc. A field is simply one of these ” e.g. your salary, your last name , or your street address. All the records of all the employees in your company make up a file, also called a database.

  4. The name given to that part of an electrical system in which electromagnetic lines of force are established.

  5. In Windows, the field is the empty line in a dialog box where you enter data.

  6. In call center jargon. A field is a single piece of data, such as an employee ID, stored in a record. The fields are organized under column headings.

Field, Cyrus W.

Cyrus Field first conceived the idea of laying a transatlantic telecommunications cable. His first and second attempts were in 1858, and were unsuccessful . His fourth attempt was a success, even though it took one hour to transmit one word. The cable went dead within a month thereafter. An electrician attempted to correct the problem by injecting 2000-Volt impulses, which fried the cable. Field tried again several more times. In 1866, he was finally successful. That cable landed at Heart's Content, Newfoundland, and was capable of transmitting telegraph messages at the rate of eight words per minute. We've come a long way since 1866.

Field Effect Transistor

A field effect transistor (FET) is composed of a single piece or channel of either P or N-type semiconductor surrounded by a ring or collar of opposite semiconductor. The collar is called the gate and the ends of the channel are called the source and the drain. As the voltage across the gate and source is varied, the resistance between the source and drain changes. A large current between the source and drain can be controlled by a small gate-source voltage.

Field Emission Displays

FED. Another way of making thin, flat, lightweight computer displays for laptops, planes, etc. The other way is called "active matrix liquid crystal display." In field emission displays, a tiny color cathode ray tube sits behind each of the many pixels in the screen. This results in a brighter picture that uses less energy than the active matrix LCD displays. See also FED.

Field Identifier

See FID.

Field Intensity

The irradiance of an electromagnetic beam under specified conditions. Usually specified in terms of power per unit area, e.g., watts per square meter, milliwatts per square centimeter.

Field Interlacing

In television, field interlacing is the process of creating a complete video frame by dividing the picture into two halves with one containing the odd lines and the other containing the even lines. This is done to eliminate flicker.

Field Measurement

Refers to both signal strength and qualitative field tests of wireless networks.

Field Programmable

The ability of a system to have changes made in its program while it is being installed ” without having to be returned to the factory. RFID tags that use EEPROM, or non-volatile memory, can be programmed after they are shipped from the factory.

Field Programmable Gate Array

FPGA. A user-configurable logic device in the form of a microprocessor. FPGAs comprise a mind-boggling variety of devices which contain memory that holds user-defined logic constructs and interconnects. Memory technologies include EEPROM, EPROM, FLASH EPROM, SRAM, fuse elements ( mainly in lower density devices), anti-fuse elements, and laser-etched metal. The memory type defines whether the configuration is maintained when power is removed (EEPROM, EPROM, FLASH, fuse, antifuse, and etched metal versions) or whether the configuration must be reloaded on during power-on (SRAM versions). Fundamental design trade-offs include the complexity of the basic cells (usually a 3-5 input look-up table and flipflop) and the richness of routing resources available to connect between cells . Modern FPGAs also include various types of signal compatibility (differential and/or low voltage inputs and outputs) and user-memory elements (either distributed or provided as array blocks). Modern designs allow the placement of preconfigured logic (microcontrollers, FIFOs, RISC processors, UARTS) for complete SOCs (systems-on-chips). FPGAS are available with huge amounts of logic (up to 5 million gates announced) and pin counts (24-500+ pins). This area of technology is very dynamic and exciting. Thanks to Ken Coffman for this definition. Ken literally wrote the book on "Real World FPGA Design with Verilog." Also see ASIC, CPLD and SOC.

Field Repairable

A characteristic of an unfortunately- decreasing number of electronic devices, that allows users or technicians to fix them where they are used ("in the field"), instead of having to send them to a centralized repair facility where esoteric parts and tools are available.

Field Replaceable Unit

Hardware component that can be removed and replaced on-site. Typical field-replaceable units include cards, power supplies , and chassis components .

Field Rheostat

A variable resistance device. The field current and consequently the strength of the electromagnetic field regulate the speed or power of the motor, or the output of the generator.

Field Sequential System

Field sequential system was the first broadcast color television system, approved by the FCC in 1950. It was later changed to the NTSC standard for color broadcasting.

Field Strength

The intensity of an electric, magnetic, or electromagnetic field at a given point. Normally used to refer to the rms value of the electric field, expressed in volts per meter, or of the magnetic field, expressed in amperes per meter.

Field Strength Meter

Electronic instrument that measures the intensity of the magnetic field.

Field Upgradable

A desirable characteristic of telecom equipment, computers, etc., that allows new features to be added and other improvements to be made, where the device is used, rather than having to return it to the manufacturer or a repair facility.

Field Wire

A flexible insulated wire used in field telephone and telegraph systems. WD-1 and WF-16 are types of field wire. Usually contains a strength member. See Field Wiring.

Field Wiring

An electrical connection intended to be made at the time of installation, in the field, as opposed to factory wired.


First In, First Out. All telephone networks are a trade-off. It's simply too expensive to build a phone network which will be ready to give everyone dial tone and a circuit ” if everyone picked up the phone simultaneously and tried to make a call. There are basically two ways of handling calls which cannot be sent on their way ” i.e. for which there's no present available capacity. First, you can "block" the call. This means giving the caller a busy or a "nothing" (also called "high and dry"). Second, you can put the call into a queue. Now you have people waiting in queue, how do you handle them? The most equitable ” the way most queues work ” is to handle the calls on the basis of First In, First Out. (First call to come in is handled first.) There are other ways of handling calls in a queue ” including First In, Last Out, by priority (e.g. which line you came in on and how much it cost, or how high you are in the corporation, etc.)

FIFO queuing also is used in some routers, although it has disadvantages in TCP/IP application. For example, if the buffer memory is full and data packets are dropped from the tail of the queue, the originating devices will assume that they are sending too rapidly and will slow down their rate of transmission. As multiple devices subsequently probe to seek the capacity of the network by sending data at higher rates, they can create another congestion condition.

FIFO also is a term used in data communications. It is a buffering scheme in which the first byte of data that enters the buffer is also the first byte retrieved by the CPU. This scheme is used in the 16550 (the UART chip which controls the serial port on most PCs and most other serial-buffering designs), because it closely mimics the way serial data is actually transmitted; that is, one bit at a time.

Fifth Generation

Fifth generation computers and telephone systems will be based on artificial intelligence. A fifth generation phone system may make far more sophisticated decisions about routing calls across networks. Those decisions may be made on how many calls have already happened so far that month, the choice of carrier by the likely quality of his connection, etc.


FIGure Shift. A physical shift in a terminal using Baudot Code that enables the printing of numbers , symbols and upper-case letters .


  1. An electrically heated wire in an evacuated glass bulb, forming one element (the cathode) of a vacuum tube.

  2. The part of an incandescent light bulb that heats and lights. Filaments are often made from Tungsten.


  1. A set of similarly structured data records (such as personnel records using a standardized form). See Field.

  2. A call center term. A logical division of the data stored on a disk or diskette; for example, employee information vs. supervisor information vs. call volume history. Files generally consist of one or more records of a certain structure.

File Allocation Table

A file allocation table is essentially a road map of the location of files on a hard disk. See FAT.

File Caching

A Novell local area network NetWare file server can service requests from workstations up to 100 times faster when it reads from and writes to the file server's cache memory (in RAM) rather than executing direct reads from and writes to the file server's hard disks.

File Extensions

MS-DOS files can have an 8-character filename followed by a period and a three-character file extension. Windows 95, Windows 98 and Windows NT files can have an up-to-256 letter filename followed by a period and then a three character extension. While most extensions are arbitrarily assigned by users or companies, some extensions are reserved for special purposes, e.g. exe, com and bat. Windows has a built in program called Explorer. When you click on that file, Explorer uses the file extension to launch an application it has associated with that extension. When you install a new application, it usually tells Explorer which file extensions it creates. Thus when you click on a file with that extension, it will launch the correct application.

Here are some common extensions:

ASP Active Server Page for use on the Internet EXE executable file

BAS Basic language file

BAT DOS executable batch file

DAT ASCII text file (usually)

COM DOS executable command file

ERR Error log file

GIF Graphic Interchange Format

HLP Help screens which appear by pressing F1 HTM HyperText Markup Language file for use on the Internet INI Initialization file

OVL Overlay file

PS Postscript file

SYS Operating system file

TAR UNIX tape archive format

Z UNIX compressed file

ZIP DOS compressed file

You'll find a definition of the extensions you're using in your Windows WIN.INI file. Here are some of mine:

txt=notepad.exe ^.txt

ini=notepad.exe ^.ini

pcx=pbrush.exe ^.pcx

bmp=pbrush.exe ^.bmp

wri=write.exe ^.wri

doc=C:\WINWORD\winword.exe ^.doc

rtf=C:\WINWORD\winword.exe ^.rtf

ppt=C:\powerpnt\powerpnt.exe ^.ppt

File Format

The way in which data is stored. The file's format is indicated by the three or four letter extension after its name. For example, Word documents end in .doc and Excel documents in .xls. An industry standard interchange file formats (IF/IFF) example is .gif for graphics. See File Extensions.

File Gap

A short length of blank tape used to separate files stored on linear magnetic tape.

File Locking

Picture a cabinet of file folders. Now I remove a folder to work on it. I make a photocopy of the folder in the cabinet and leave the original. You come along and remove the original because you want to work on it. You make changes and replace the changed copy in the cabinet. Ten minutes later I pull your file out and replace it with mine. Bingo, all your changes are lost. But let's say when I remove the file to work on it, I staple the remaining folder shut. That's a message to anyone else ” including you that you shouldn't mess with the file. When I return, I unstaple the file, and add my changes. Now it's ready for you to do your thing. File locking ensures that a file will be updated correctly before another user, applications, or process will be allowed to write to the file. When a file is locked, no one else can write to it. Without file locking, one user could overwrite the file update of another user. In contrast to file locking, record locking allows many users to access the same file at once, but have only one access the record. See also ATTRIB and Record Locking.

File Maintenance

The job of keeping your data base files up to date by adding, changing or deleting data.

File Management

The system of rules and policies for maintaining a set of files ” including how files can be created, accessed, retrieved and deleted.

File Server

A file server is a device on a local area which "serves" files to everyone on that local area network (LAN). It allows everyone on the network to get to files in a single place, on one computer. It typically is a combination computer, data management software, and large hard disk drive. A file server directs all movement of files and data on a multi-user communications network, namely the LAN. It allows the user to store information, leave electronic mail messages for other users on the system and access application software on the file server ” e.g. word processing, spreadsheet. In computer telephony applications, potentially many users or voice channels need to access data on a file server. The file server may therefore present a significant bottleneck for computer telephony especially if it is used to store large files, such as voice prompts. The ability for the file server to handle the transaction load planned for your computer telephony application is therefore a key design consideration and issue to test.

File Server Console Operator

A user or a member of a group to whom a Novell NetWare SUPERVISOR delegates certain rights in managing the file server. A file server console operator has rights to use FCONSOLE to broadcast messages to users, to change file servers, to access connection information, to monitor file/lock activity, to check LAN driver configurations and to purge all salvageable files.

File Service Protocol

See FSP.

File Sharing

A topology-independent feature of Apple Macintosh's System 7 operating system which allows users to share files and folders on their disks with other users across the LAN. File sharing is slow but acceptable for sharing small numbers of files among small groups. For larger networking, the user must consider AppleShare, Netware, Vines, etc.

File Spanning

Creating one compressed file that contains many files, typically retrieved from many removable media, e.g. floppy disks.

Filed Trail

Also known as Beta Test.

File Transfer Protocol

FTP. A service that supports file transfer between local and remote computers, including the Internet. FTP supports several commands that allow bidirectional transfer of binary and ASCII files between computers. The FTP client is installed with the TCP/IP connectivity utilities. See also FSP, FTP, and File Transfer Protocols.

File Transfer Protocols

One problem with transmitting information over phone lines is the noise on the phone line. One way to overcome the problem of noise is a file transfer protocol. The idea is simple: send your information in bundles (called packets). Accompany those packets with a special number derived in some way from the information in the packet. Send it all to the other end. Have the computer at the other check the number and see if corresponds to the packet. If not, send a signal back, saying "Something went wrong. Please send the packet of information back again."

Most asynchronous file transfer protocols use some form of error detection, typically checksum or cyclic redundancy check (CRC). Both the checksum and the CRC are values derived from the data being sent (or received) according to mathematical algorithms. The protocol sends the value long with the information (the bits) in the packet. The receiving program compares with the check values with the values it calculates. If the check values do not match, the receiver asks the sending computer to retransmit the packet. Older protocols required a positive acknowledgement (an ACK) before they sent another packet. But newer protocols allow transmission of several packets before they receive an acknowledgement. This is particularly useful for circuits with long delays, especially satellites . See also XModem.

File Transfer Software

Software to transmit files between computers, over phone lines or over a direct cable connection between the two computers.


Bit Stuffing . See Fill Bits.

Fill Bits

Also known as Stuff Bits. Fill bits are used to fill up a data packet or a frame, which must be of a certain minimum size, or perhaps of a certain specific size . If the transmitting device doesn't have enough bits to fill the packet, it stuffs in some nonsense bits which the receiving device tosses away. This process is known as "bit stuffing." "Keep alive bits" are fill bits used to keep a session alive between two devices across a circuit. Without the "keep alive bits," the receiving device would "time out," thereby aborting the data communication session.

Filler Panel



A computer imaging term. Designated areas that are flooded with a particular color. Most paint packages let you create geometric shapes in filled form. All packages also let you fill irregular closed regions. Two types of such fills exist: A seed fill floods all connected regions with the color specified by the mouse or stylus pointer; a boundary fill floods a color until the algorithm encounters a specified boundary color.


First In, Last Out.


  1. A device which transmits a selected range of energy. An electrical filter transmits a selected range of frequencies, while stopping (attenuating) all others. It is used to suppress unwanted frequencies or noise, or to separate channels in communications circuits. Such a filter might be called a BANDPASS filter. You can also use a filter to remove certain characters you might be receiving over a data communications channel, for example control characters or higher-order nonstandard ASCII bits.

  2. An operating parameter used in LAN bridges and routers that when set will cause these devices to block the transfer of packets from one LAN to another. Filters can be set to prevent the internetworking of several types of messages. They may be set to block all packets originating from a specific destination, called source address filtering, or all packets heading for a particular destination, called destination address filtering. Filters may also be set to exclude packet of a particular protocol or any particular filed in a LAN packet.

  3. See TAPI 3.0.


  1. A process used in both analog and digital processing to pass one frequency band while blocking others or visa-versa. Filters can be designed to remove information content such as high or low frequencies, for example, or, in image processing, to average adjacent pixels, creating a new value from two or more pixels. "Tap" refers to the number of adjacent lines or pixels considered in this process. MPEG, for instance, makes use of a 7-tap filter.

  2. Bridges can reduce LAN congestion through a process of filtering. A filtering bridge reads the destination address of a data packet and performs a quick table lookup in order to determine whether it should forward that packet through a port to a particular physical LAN segment. A four-port bridge, for instance, would accept a packet from an incoming port and forward it only to the LAN segment on which the target device is connected; thereby, the traffic on the other two segments is reduced and the level of traffic on the those segments is reduced accordingly . Filtering bridges may be either programmed by the LAN administrator or may be self-learning. Self-learning bridges "learn" the addresses of the attached devices on each segment by initiating broadcast query packets, and then remembering the originating addresses of the devices which respond. Self-learning bridges perform this process at regular intervals in order to repeat the "learning" process and, thereby, to adjust to the physical relocation of devices, the replacement of NICs (Network Interface Cards), and other changes in the notoriously dynamic LAN environment.

Filtering Agent

A new form of smart agent whose basic job is to keep away all the stuff you don't want and find the stuff you do want ” such as information gleaned from the Internet. See also V-Chip.

Filtering Bridge

See Bridge.

Filtering Traffic

This is the process of selecting which traffic will be allowed into a certain portion of a network, such as the wide area network. It is also the process of determining which traffic is transmitted first, then next, and so on. The traffic is compared to a filter, or a set of specifications, to determine if it can pass through or not.


Field inspection notice.

Final Draft

Lisa Kiell's strange idea of completing a transaction. See Oxymoron.

Final Trunk Group

A last-choice trunk group that receives overflow traffic and which may receive first-route traffic for which there is no alternate route.

Find Me Service

An AIN version of call forwarding, allowing the forward numbers to be programmed or re-programmed from any location. Additionally, priority access can be extended to specific callers based on password privilege. For instance, only highly privileged callers would be forwarded to your cell phone, in consideration of the high cost of airtime.


The user interface portion of the Apple Macintosh operating system. Unlike running Windows on top of DOS, tight integration of the finder and system requires both to be running.


  1. A standard protocol specified in RFC-742. A program implementing this protocol lists who is currently logged in on another host. In short, finger is a computer command that displays information about people using a particular computer, such as their names and their identification numbers.

  2. Also known as a tine. An individual digital channel of a wireless rake receiver. A rake receiver can support a number of tines, which can be combined to form a stronger received signal.

Finger Wheel

The actual "dial" on a rotary dial phone is called the finger wheel.

Finite State Machine

A computer system with a defined set of possible states and defined transitions form state to state. Given the same inputs, two identical state machines will change states identically.


Federal Information Processing Standard. See also FIPS PUBS nn.


Various standards for data communications.


Bus and tag channel interface for IBM 360/370 mainframes (multidrop, two copper cables)one for data, one for control information, 1.5-4.5 Megabytes per second with a maximum distance of 121 meters .


Fast Infrared. This infrared standard from IrDA supports synchronous, wireless communications at 4Mbps at a distance of up to one meter.


To discharge someone. In Scotland during medieval times, if your clan wanted to get rid of you, but not kill you, they would set fire to your house. Hence, the origin of the expression, "to get fired." The story goes that in the early part of the 20th century, if an NCR salesman lost an order, when he returned to his office, they put his desk out on the front lawn and burned the desk. Then they " fired " the salesman.

Fire Break

A material, device, or assembly of parts installed along a cable, other than at a cable penetration of a fire barrier , to prevent the spread of fire along a cable.


In the late 1700s the larger American cities, such as Philadelphia, laid pipes to bring in water. This was not for drinking, but for firefighting purposes. The pipes were made out of hollowed out logs placed end to end and buried under the streets . When there was a fire, the firemen would punch through to the pipe to pump the water out, and once finished would plug the hole using a wooden stake of the proper size. Hence the name, "fireplug."

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133

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