F facilities administration and control PBX feature that permits the subscriber to assign individual features and privileges to the stations. facilities assurance reports Feature that permits a subscriber to obtain an audit trail of data produced by the automatic circuit assurance feature of some PBXs. The audit trail identifies the trunk circuit, time of the referral, nature of the problem and, if a test was made, the outcome of that test. facilities restriction level Refers to the types of calls a PBX user is authorized to make. facility network A network in which LANs and network segments within a building or campus are interconnected to function as one, transparent, computing platform. facsimile (FAX) A system for the transmission of images in which the image is scanned at the transmitter, reduced to signal form, delivered at the receiving station, and printed on some medium. facsimile mail module interface Interface between a PBX and a facsimile mail module; facsimile transmits a picture, drawing, or document over a voiceband. facsimile server A server that allows multiple network users to send or receive facsimile transmissions through the same device. The facsimile server is typically a dedicated PC, but can also be a facility that operates in background mode on a non-dedicated workstation. fading Reduction in signal intensity of one or all elements of a microwave or radio signal. fail soft The ability of a system to detect component failures and modify its processing temporarily to prevent irretrievable loss of data or equipment. fallback (modem) Mode of operation in which a modem communicates at a speed slower than its rated speed when line conditions are unsatisfactory. fallback procedures Predefined operations (manual and/or automatic) invoked when a fault or failure is detected in a system. FAQ Frequently asked questions, a suggested-reading document maintained by most mailing lists and newsgroups to avoid repeating old news for each newbie. FAR Federal Acquisition Regulations. fault tolerance Ability of a computer or network system to continue operating even in the event of software errors or hardware malfunctions. fault tolerant server A dedicated PC that safeguards critical data and maintains user productivity in the event of a failure on the network via duplication of data and the incorporation of backup devices. faulty trunk report A feature that allows a station user to report about a noisy or faulty trunk line, even while the connection is on. FAX See facsimile. FBA Fixed Block Architecture. FBAM See flexible board address mapping. FCC See Federal Communications Commission. FCS See frame check sequence. FD or FDX (full duplex) See channel. FDDI See fiber distributed data interface. FDM See frequency-division multiplexing. FDMA See frequency-division multiple access. FDOS Floppy Disk Operating System. feature extraction The optical character recognition (OCR) technique used by "omnifont" OCR software. feature group Four separate switching arrangements available between local exchange carriers and long distance carriers for customers who wish to make toll calls. 2. Feature Group A (FGA) offers entry to the local exchange carrier's network through a subscription-type line connection rather than a trunk; the carrier requires the customer to dial a local number to reach the other common carrier (OCC), then dial an identification number and the long distance number of the required party. 3. Feature Group B (FGB) resembles FGA (in numbers dialed), but provides a higher quality trunk line connection at as higher cost. 4. Feature Group C (FGC), is the traditional toll service offered by local carriers to AT&T prior to divestiture. 5. Feature Group D (FGD) permits customers to reach the long distance carrier by dialing 1 plus the telephone number being called. Federal Communications Commission (FCC) A U.S. government agency that regulates interstate and foreign wire, radio and television communications. Federal telecommunications system The private network used primarily by the civilian agencies of the federal government to call other government agencies as well as phones connected to the public network. feedback That part of an output signal that is returned to the input side of a device. FEP See front-end processor. FFOL FDDI follow-on LAN. fiber distributed data interface (FDDI) An ANSI standard for a 100M bps fiber-optic LAN using "acounter-rotating" token-ring topology. fiber mile The number of route miles along a telecommunications path multiplied by the number of fibers along that path. fiber optic cable Cable made from thin strands of glass through which data in the form of light pulses is transmitted. Used for very high-speed transmission over medium to long distances. fiber optics High-speed transmission using light to send images (in telecommunications: voice or data) through a flexible bundle of glass fibers. fiber-optic cable Data-transmission medium comprising a central glass (or plastic) fiber, glass cladding, and a plastic outer sheath. fiber-optic inter-repeater link (FOIRL) An IEEE 802.3 standard for Ethernet transmissions via fiber-optic cable. fiber-optic waveguides Thin filaments of glass or other transparent materials through which light beams can be transmitted for long distances by means of multiple internal reflections. fiber-optics High speed transmission using light to send images (in telecommunications: voice or data) through a flexible bundle of glass fibers. FICON File conversion (software). Fidonet A hobbyist BBS network with an e-mail gateway and other links to the Internet under development. FIFO See first in/first out. figures shift A control character in Baudot code indicating that subsequent characters are uppercase. Also, a physical shift in a teletypewriter that enables the printing of numbers, symbols, and characters as uppercase. See also letters, shift. file server A key part of a LAN -- typically a combination of computer, data management software, and hard disk storage that directs all movement of files and data on the LAN and gives each network user entry to those stored files. file transfer protocol (FTP) Commands used in a data network which perform file and directory operations. FTP allows file transfer from an IP host to an IP client without requiring the client to mount the host's file system. filter Device that transmits a certain range of frequencies while suppressing unwanted frequencies or noise, or separating channels in communications circuits. finger An internet standard protocol and UNIX command that lists who is currently logged on to another host. FIPS Federal Information Processing Standards. firewalls Software and hardware gatekeepers installed between your computer and other computers, requiring a special password to access, and blocking out unwanted transactions. firmware Programs retained in semipermanent storage such as PROM or EPROM. first in/first out (FIFO) A queuing technique in which the first call to be retrieved is the call that has been in the queue the longest. first read rate The percentage of times a bar code scanner gets it right in the first pass. A measurement of quality. fixed beam scanner A stationary bar code scanner. fixed night service See also night service. flame An USENET news article, written as a personal attack on another internet user. flash See can flash. flat rate Telephone tariff where there is no charge for local calls; the rental fee covers unlimited local calls. flatbed A scanner design in which the document is placed on the scanner's bed, either manually or by an automatic document feeder, and remains in one position during scanning. flexible board address mapping (FBAM) The ability to have several boards in one system overlap at the same base address. flexible intercept Operator intercept service can be assigned to any extension for any reason (i.e., unassigned number or temporary disconnect). flexible line ringing PBX feature allowing various phones to have different ringing for different types of calls, (i.e., in-house calls have one type of ringing while outside calls or intercom calls have different ringing signals). flexible night service The ability of the attendant to change night service assignments associated with extensions or hunt groups. See also night service. flexible numbering of stations PBX feature that permits the subscriber some flexibility in numbering station extensions. flexible route selection (FRS) Centrex method of accomplishing the least expensive route to complete a call. flooding A process in which a bridge broadcasts the first packet it receives with an unknown destination address to all LAN locations. When it receives a reply from the remote device, it updates its routing table. flop To turn over an image to its mirror image, i.e., from facing left to facing right. Not to be confused with reverse, which means convert the image from positive to negative or vice versa. FLOPS Floating-point operations per second. flow control Method in which information is controlled in a network to prevent loss of data when the receiving buffer is nearing capacity. flux Also referred to as lines of force; the measurable effect of a magnetic field. flying spot scanner A scanning device that uses a point of light passed over a document to convert it to electronic signals. FM See frequency modulation. FNP Front-end Network Processor. FOCAL Programming language (Digital Equipment). FOIRL See fiber-optic inter-repeater link. footprint 1. Total area on the earth's surface where signals from a satellite can be received, usually shown as concentric contour lines on a map which represent the range of the signal and its decreasing power as it moves more distant from the center. 2. The actual space on a work surface that a device occupies. forced account code Mandatory entering of account codes is required for outgoing calls. See also account code. foreign exchange (FX) Term used to indicate service from any central office other than the central office that ordinarily serves a particular location. form 1. A paper form used for printing. 2. A screen display designed for a particular application. form feed The ability of a printer to move continuous rolls of paper into the proper position to print one page after another. forms processing The ability of software to accept scanned forms and extract data from the boxes and lines to populate databases. Usually based on "zoned" OCR, and often includes the ability to "drop-out" the form itself to improve OCR accuracy and save storage space. FORTRAN FORmula TRANslation; programming language for computers. forward channel The communications path that carries data or voice from the station that initiated the call. forward error correction Data transmission where redundant bits produced at the transmitted end are used at the receiving terminal to detect, locate and correct any errors before delivery to the local data communications link. FOTS Fiber optic transmission systems. See fiber optic waveguides. four-wire The links available in full-duplex mode without requiring additional multiplexing. four-wire channel Transmission path containing two pairs of wires and used for full-duplex transmission. four-wire circuit Circuit with two pairs of conductors, one for outbound channels and the other for returning channels. FPDU File Protocol Data Unit. FPGA Field programmable array technology. fractional T1 (FT1) The use of bandwidth in 64K bps (DS0) increments up to 1.544M bps from a T1 facility. FRAD Frame Relay Access Device. frame One complete cycle of events in time-division multiplexing, usually including a sequence of time slots for the various subchannels and extra bits for protocols. frame buffer A large section of memory used to store an image to be displayed on-screen as well as parts of the image that lie outside the limits of the display. frame check sequence (FCS) An error-detecting code inserted as a field in a block of data to be transmitted. frame grabber A device that accpts standard TV signals and digitizes the current video frame into a bitmap image. frame relay A high-speed packet switching (10 times X.25) technology based on LAPD protocol. framing An error control procedure with multiplexed digital channels, such as T1, where bits are inserted so that the receiver can identify the time slots that are allocated to each subchannel. Framing bits may also carry alarm signals indicating specific alarms. FRAN Frame relay access node. frequency The number of complete cycles per unit of time. frequency bands Portion of the electromagnetic spectrum within a specified upper- and lower-frequency limit. Also called frequency range. frequency hop A spread-spectrum communications technique in which portions of a digital transmission occur at random frequencies in order to escape detection of suppression. Reception requires the ability to follow the random hops, maintain synchronization, and demodulate the signal. frequency modulation (FM) The technique of varying the frequency of a carrier wave in direct proportion to the strength of the input signal while maintaining a constant amplitude. frequency response The reaction of frequencies to the circuit response. frequency shift keying (FSK) Frequency modulation of a carrier by a modulating signal that varies between a fixed number of discrete values (a digital signal). frequency spectrum designation (VLF) very low frequency below 30 KC/s (0.03 MC/s). (LF) low frequency 30 to 300 KC/s (0.03 MC/s). (MF) medium frequency 300 to 3000 KC/s (0.03 to 3 MC/s). (HF) high frequency 3000 to 30,000 KC/s (3 to 30 MC/s). (VHF) very high frequency 30 to 300 MC/s. (UHF) ultrahigh frequency 300 to 3000 MC/s. (SHF) superhigh frequency 3000 to 30,000 MC/s. (EHF) extremely high frequency 30,000 to 300,000 MC/s. frequency-division multiplexing (FDM) A system in which the available transmission frequency range is divided into narrow subchannels for use by a number of low-speed devices. frequency-division multiplexing access (FDMA) Technique for sharing a single transmission channel among two or more users by allocating each an exclusive frequency band within the channel. front-end network A network, often a LAN, connected to a front-end processor or a computer's communications port. front-end processor (FEP) A communications processor that attaches to host mainframe via a byte/block multiplexer channel or selector channel, and handles all the functions associated with establishing a communications link and passing data to and from the network. FRS See flexible route selection. FSK See frequency-shift keying. FT1 See Fractional T1. FTAM 1. File access management protocol. 2. File Transfer, Access, and Management OSI standard defined in ISO 8571. FTF File Transfer Facility. FTP See file transfer protocol. FTP Commands A set of commands and responses that flow between a user-FTP and a server-FTP on their control connection. FTTF Fiber-to-the-feeder. full period Relates to private line service rented for the exclusive use of a single customer for an entire month. full-duplex (FDX) transmission Data transmission in both directions simultaneously. See also channel. fully restricted stations A fully restricted station is prohibited from placing calls. See also restriction. functional split A division within an automatic call distributor (ACD) that allows incoming calls to be directed from a specific group of trunks to a specific group of agents. functional test A test carried out while a circuit or equipment is operating under normal working conditions. FX See foreign exchange.