Telecommunications terms starting with F

396 terms

frequency coherence See phase coherence.
frequency compatibility 1. Of an electronic device, the extent to which it will operate at its designed performance level in its intended operational environment (including the…
frequency departure The difference between the instantaneous frequency of a digital signal and the long-term average frequency of that signal. [T1.Rpt17-1993] 2.
frequency deviation The amount by which a frequency differs from a prescribed value, such as the amount an oscillator frequency drifts from its nominal frequency. 2.
frequency dispersal An electronic counter-countermeasure (ECCM) in which communications nets' operating frequencies are widely separated from each other, causing a…
frequency displacement The end-to-end shift in frequency that may result from independent frequency translation errors in a circuit.
frequency distortion Synonym amplitude-vs.-frequency distortion.
frequency diversity Transmission and reception in which the same information signal is transmitted and received simultaneously on two or more independently fading carrier…
frequency drift An undesired progressive change in frequency with time. Note 1: Causes of frequency drift include component aging and environmental changes.
frequency fluctuation A short-term variation, with respect to time, of the frequency of an oscillator.
frequency flutter A deviation of frequency that generally results from irregular motion of the recording medium during the recording, duplication, or reproduction. [T1.
frequency frogging The interchanging of the frequencies of carrier channels to accomplish specific purposes, such as to prevent feedback and oscillation, to reduce…
frequency guard band A frequency band deliberately left vacant between two channels to provide a margin of safety against mutual interference.
frequency hopping [The] repeated switching of frequencies during radio transmission according to a specified algorithm, to minimize unauthorized interception or jamming of…
frequency hour One frequency used for one hour regardless of the number of transmitters over which it is simultaneously broadcast by a station during that hour. [47CFR]
frequency instability See frequency stability.
frequency lock The condition in which a frequency-correcting feedback loop maintains control of an oscillator within the limits of one cycle.
Frequency Modulation (FM) Modulation in which the instantaneous frequency of a sine wave carrier is caused to depart from the center frequency by an amount proportional to the…
frequency of optimum traffic (FOT) Synonym FOT.
frequency of optimum transmission (FOT) See FOT.
frequency offset The difference between the frequency of a source and a reference frequency.
frequency prediction A prediction of the maximum usable frequency (MUF), the optimum traffic frequency, and the lowest usable frequency (LUF) for transmission between two…
frequency range A continuous range or spectrum of frequencies that extends from one limiting frequency to another.
frequency response See insertion-loss-vs.-frequency characteristic.
frequency response curve A plot of the gain or attenuation of a device, such as an amplifier or a filter, as a function of frequency.
frequency scanning Conducting a search for signals over a band or range of frequencies by means of a manually or automatically tuned receiver. Note: The tuning rate, i.e.
frequency sharing The assignment to or use of the same radio frequency by two or more stations that are separated geographically or that use the frequency at different…
frequency shift Any change in frequency. 2. Any change in the frequency of a radio transmitter or oscillator.
frequency source See frequency standard.
frequency spectrum See electromagnetic spectrum.
frequency spectrum congestion The situation that occurs when many stations transmit simultaneously using frequencies that are close together, i.e.
frequency stability The degree to which variations of the frequency of an oscillator deviate from the mean frequency over a specified period of time.
frequency standard A stable oscillator used for frequency calibration or reference. Note 1: A frequency standard generates a fundamental frequency with a high degree of…
frequency synthesizer A device that produces frequencies that are phase coherent with a reference frequency.
frequency tolerance The maximum permissible departure by the center frequency of the frequency band occupied by an emission from the assigned frequency, or by the…
frequency translation The transfer of signals occupying a specified frequency band, such as a channel or group of channels, from one portion of the frequency spectrum to…
frequency-analysis compaction Data compaction accomplished by using an expression composed of a number of different frequencies of different magnitudes to represent a particular curve.
frequency-change signaling A signaling method in which one or more discrete frequencies correspond to each desired significant condition of a code.
frequency-derived channel A channel derived by dividing an allocated or available bandwidth over a medium into two or more portions, each usable separately.
frequency-division multiple access (FDMA) The use of frequency division to provide multiple and simultaneous transmissions to a single transponder.
frequency-division multiplexing (FDM) The deriving of two or more simultaneous, continuous channels from a transmission medium by assigning a separate portion of the available frequency…
frequency-exchange signaling Frequency-change signaling in which the change from one significant condition to another is accompanied by decay in amplitude of one or more frequencies…
frequency-hopping spread spectrum A signal structuring technique employing automatic switching of the transmitted frequency.
frequency-shift keying (FSK) Frequency modulation in which the modulating signal shifts the output frequency between predetermined values.
frequency-shift modulation Synonym frequency-shift keying.
frequency-shift signaling Synonym frequency-shift keying.
frequency-shift telegraphy Telegraphy by frequency modulation in which the telegraph signal shifts the frequency of the carrier between predetermined values. [NTIA] [RR]
frequently asked questions See FAQ file.
Fresnel diffraction pattern Synonym near-field diffraction pattern.
Fresnel reflection In optics, the reflection of a portion of incident light at a discrete interface between two media having different refractive indices.
Fresnel zone In radio communications, one of a (theoretically infinite) number of a concentric ellipsoids of revolution which define volumes in the radiation pattern…
front-end noise temperature A measure of the thermal noise generated in the first stage of a receiver.
front-end processor (FEP) A programmed-logic or stored-program device that interfaces data communication equipment with an input/output bus or memory of a data processing computer.
front-end security filter 1. [A] security filter logically separated from the remainder of an information system (IS) to protect system integrity.
front-to-back ratio 1. Of an antenna, the gain in a specified direction, i.e., azimuth, usually that of maximum gain, compared to the gain in a direction 180° from the…
FSDPSK Abbreviation for filtered symmetric differential phase-shift keying.
FSK Abbreviation for frequency-shift keying.
FTAM Abbreviation for file transfer, access, and management.
FTP File Transfer Protocol (ADP/Internet term).
FTP archive A collection of files that are available by using file transfer protocol (FTP). Synonyms file archive, file site.
FTP mail A method of accessing and retrieving FTP-based files via e-mail.
FTS (1) Flight Test Summary (2) Federal Telephone Service
FTS2000 Abbreviation for Federal Telecommunications System 2000. The designation for a defunct Federal telecommunications contract replaced by the contract…
FTS2001 Abbreviation for Federal Telecommunications System. A contract to provide a consolidated telecommunications capability to support Federal agencies with…
full carrier A carrier that is transmitted without reduction in power, i.e., a carrier that is of sufficient level to demodulate the sideband(s).
full carrier single-sideband emission A single-sideband emission without reduction of the carrier. [NTIA] [RR]
full duration at half maximum (FDHM) Full width at half maximum in which the independent variable is time. See full width at half maximum.
full load level (FLL) The peak voltage level of a nominal 400-Hz sine wave required to excite the analog-to-digital converter of the transmit channel unit to the extremes of…
full modulation In an analog-to-digital converter, the condition in which the input signal amplitude has just reached the threshold at which clipping begins to occur.
full processing All processing functions required to recover the information bits from a received signal.
full width at half maximum (FWHM) An expression of the extent of a function, given by the difference between the two extreme values of the independent variable at which the dependent…
full-duplex (FDX) circuit A circuit that permits simultaneous transmission in both directions.
full-duplex (FDX) operation Synonym duplex operation.
full-motion operation In television, a video frame update rate that provides the appearance of full motion without flicker or smear problems.
fully connected mesh network See network topology.
fully connected topology See network topology.
fully intermateable connectors Connectors from one source that mate with complementary components from other sources without mechanical damage and with transmission properties…
fully qualified domain name (FQDN) The complete name of a specific computer on the Internet, consisting of the computer's host name and its domain name.
function signal A set of signal elements that is used to transmit or represent a function-control character that actuates a control function, such as carriage return…
functional component (FC) In intelligent networks, an elemental call-processing component that directs internal network resources to perform specific actions, such as collecting…
functional profile A standardization document that characterizes the requirements of a standard or group of standards, and specifies how the options and ambiguities in the…
functional signaling In an integrated services digital network (ISDN), signaling in which the signaling messages are unambiguous and have clearly defined meanings that are…
functional signaling link A combination of a communications link and the associated transfer control functions.
Functional Testing The portion of testing in which the advertised features of a system are tested for correct operation.
functional unit 1. An entity of hardware, software, or both, capable of accomplishing a specified purpose. 2. A functionally distinct part of a basic component [ITSEC].
functionality The ability of equipment to operate as expected during actual service conditions in a central office. [T1.304-1989]
functionality class A predefined set of complimentary security enforcing functions capable of being implemented in a Target of Evaluation [ITSEC].
fundamental Of a periodic wave, the sinusoidal component, i.e., Fourier component, having the lowest frequency.
fundamental mode The lowest order mode of a waveguide. Note: In optical fibers, the fundamental mode is designated LP01 or HE11.
furcate Synonym break out.
Fuse A safety device consisting of a short length of relatively fine wire, mounted in a holder or contained in a cartridge and connected as part of an…
fused silica Synonym vitreous silica.
Fusion The combining of lighter elements into heavier ones. For lighter elements (e.g., hydrogen, helium) this process releases energy.
fusion splice In fiber optics, a splice created by localized heating of the ends of the two fibers to be joined.
FWHM Abbreviation for full width at half maximum.
FX Abbreviation for fixed service, foreign exchange service.