[F]

Facility – A transmission path between two or more locations without terminating or signaling equipment. [Addition of terminating equipment would produce either a channel, a central office line or a trunk. Various types of signaling would also be used depending on the application.}

Facsimile - (1) A system for the transmission of a picture, drawing or other document by converting it into coded electrical signals which are subsequently converted into a replica of the original image at the receiving end. (2) The replicated image of picture, drawing or document. (See fax.)

Facsimile transmission - An electronic means for transferring a precise reproduction.

Family One Service - One of the new definitions of service level to be provided by IT Communications Services. ITD will provide a "quick response" to service requests in this category. This means the service will be provided right at the point of contact with ITD.

Family Two Service - One of the new definitions of service level to be provided by IT Communications Services. ITD will place service requests in this category on a "fastpath." This means the service will be provided within five days of the point of contact with ITD.

Family Three Service - One of the new definitions of service level to be provided by IT Communications Services. ITD will perform a "coordinated request" for service requests in this category. This means the service will require a number of ITD staff to be involved and it will take a greater amount of time to provide the service.

Fault tolerance - The level of ability within a program or system to operate properly even if errors occur.

Fax - (1) Abbreviation for facsimile. (2) Reference to either the service or the actual machines by which a copy of a document or picture may be transmitted. (3) A verb meaning to send an electronic image.

Feature groups - The different types and qualities of public switched network connection between local telephone companies and long distance companies.

Feature group A (FGA) - (1) A service that uses off-network access lines (ONAL). (2) A level of dial-up service in which subscribers have to dial a full local subscriber number to connect to the IXC, then have to key out (using DTMF) their personal authorization code followed by the distant number required.

Feature group B (FGB) - (1) A dial-up service that gives no hardware answer code which means call timing may be inaccurate. (2) A service that uses off-network access trunks (ONAT) which eliminate most off-network access line difficulties and greatly improve transmission quality (for local offices).

Feature group C (FGC) - (1) A dial-up service that uses off-network access trunks which eliminate most off-network access line difficulties and greatly improve transmission quality (for local tandem offices).

Feature group D (FGD) - (1) A dial-up service employing a coding method to enable telephone customers to choose their long distance network and use the same number of digits whichever carrier chosen. (2) Uses off-network access trunks (ONAT). See Equal Access.

Federal Communications Commission (FCC) - Government agency established by the Communications Act of 1934 which regulates all interstate communications.

Federal Telecommunications System (FTS) - A government communications system administered by the General Services Administration (GSA), covering all 50 states plus Puerto Rico and the Virgin Islands; provides services for voice, teletypewriter, facsimile and data transmission.

Feedback - (1) Return of part of the output of a machine, process or system to the computer as input for another phase; typically used for surveillance, self-correcting maintenance or control purposes. (2) Means of comparing or providing actual performance which can be compared with planned performance.

Fiber optics - (1) A means of providing a high-speed transmission, using light to send images through a flexible bundle of glass fibers. (2) The use of light as the primary medium in an actual application.

Fiber-optic transmission system (FOTS) - A means of sending data by coded light pulses through small diameter glass fibers. [Information is transferred by modulating the transmitted light. These modulated signals are detected by light-sensitive semiconductor devices (photodiodes).]

Fiber-optic cable – A bundle of thin filaments of glass or other transparent materials used as the medium for transmitting coded light pulses that represent data, images or sound.

Fifo (first in-first out) queuing – Method where the next item to be retrieved is the item which has been waiting the longest.

File – (1) An organized, named collection of records treated as a unit. (2) The storage media on which these records are kept.

File server – A station or microprocessing computer dedicated to providing file and mass data storage services to the other stations on the local network. [Often found in Local Area Network (LAN) applications.]

Firmware – Computer programs that are embodied in a physical device that can form part of a machine. [Contrasted with software, which refers to the entire set of programs, procedures and documentation associated with a system, specifically computer programs, which are portable from one machine to another.]

Flat rate – (1) Fee for a product or service that is not dependent on usage. (2) Telephone tariff in which no charges are levied for local calls. (3) A rental charge which covers unlimited or equipment usage.

Flow control – The procedure for controlling the rate of transfer of packets between two designated points in a data network; used to prevent data loss during transmission.

Footprint – (1) That portion of the earth’s surface illuminated by a narrow beam from a satellite. (2) Floor or work space occupied by a given unit of equipment.

Foreign exchange (FX) – A circuit that connects a subscriber in one exchange with a central office in another exchange.

Foreign exchange line – Line offered by a common carrier in which the user in one central office is assigned a telephone number belonging to a remote central office to minimize long distance charges. [Charges for these lines vary from carrier to carrier.]
forward channel – Communications path carrying voice or data from the originating caller to the terminating destination.

Forward error correction – Technique for regenerating lost data transmissions or errored messages; retransmission of any information by the transmitter. [Typically, this is accomplished by adding bits to each transmitted character or code clock using a predetermined algorithm. It doesn't need a feedback channel, and therefore may be used with a one-way transmission system.]

Frequency division multiplexing (FDM) – Method of transmitting two or more signals by dividing the available transmission frequency into narrower bands and using each as a separate channel.

Frequency modulation (FM) – Transmission method in which the frequency of the carrier wave is changed to correspond to changes in the signal wave.

Full duplex – See duplex.