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 RadioShack Consumer Electronics Glossary: F

F
Communications: see Frequency.
Electronics: see Farad or Frequency.
Measurement: see femto- (f-).
Weather: see Fahrenheit.
 
F/# (F2, F 2.8, F/3, etc.): see F-Stop.
 
Fahrenheit (F)
Weather: A temperature scale where water at sea level has a freezing point of +32°F and a boiling point of +212°F. More commonly used in areas that observe the english system of measurement. Created in 1714 by Gabriel Daniel Fahrenheit (1696-1736), a German physicist, who also invented the alcohol and mercury thermometers.
 
FAQ
Acronym: Frequently Asked Questions
Internet: A document (usually on a website) that provides answers to commonly-asked questions.
 
Farad
DIY, Electronics: The measurement unit of capacitance, named after Michael Faraday. One farad is the capacitance of a capacitor that gives a difference of potential of one volt when charged with one coulomb.
 
FCC
Acronym: Federal Communications Commission
Communications: The government agency responsible for regulating telecommunications in the United States.
 
FDDI
Acronym: Fiber Distributed Data Interface
Networking: A standard for transmitting data on fiber optic cables at a rate of around 100 Mbps (10 times as fast as Ethernet, about twice as fast as T-3).
FDMA
Acronym: Frequency Division Multiple Access
Telephony: A method of radio transmission that allows multiple users to access a group of radio frequency bands without interference.
 
femto- (f-)
Measurement: SI / Metric unit of decimal measurement, equal to 10-15 or 0.0000000000001.
 
Ferrite
Electronics: A powdered, compressed and sintered magnetic material having high resistance, resulting in low eddy current losses at high frequencies.
 
Ferrite Bead
Electronics: A component that will increase the inductance of a wire that runs through the bead.
 
Ferrite-core Inductor: see Inductor, Ferrite-core.
 
Ferrous
Metal Detectors: A material composed of and/or containing iron.
 
Ferrous Oxide
Metal Detectors: An oxidized particle of iron which becomes non-conductive and makes up the natural negative ground mineral matrix. Hematite, which is also an iron oxide, will respond as positive or metallic.
 
FET
Acronym: Field- Effect Transistor
Electronics: A voltage-controlled transistor in which the source-to-drain conduction is controlled by the gate-to-source voltage. There are two primary types of FET: MOSFET (Metal-Oxide-Semiconductor Field- Effect Transistor) and J-FET (Junction Field- Effect Transistor).
 
Few
Weather: The amount of sky cover for a cloud layer between 1/8th and 2/8ths, based on the summation layer amount for that layer.
 
FHSS
Acronym: Frequency Hopping Spread Spectrum
Telephony: A transmission method used in spread spectrum radio systems that converts the data stream into a stream of packets.
 
Fiber-optic
Cables: A technology that converts an audio and/or video signal to a digital signal and transmits by way of bursts of light.
 
Field Effect Transistor: see FET.
 
Field of View
Binoculars, Video: The width of the viewable image; expressed either as an angle or as "meters at 1000 meters". The measurement "# meters at 1000 meters" indicates that the binoculars or video device can resolve two objects # meters apart at 1000 meters. To convert:
(field of view angle)° = (meters at 1000 meters) / 17.5 = 3 x (feet at 1000 feet) / 17.5
 
Figure-eight
Audio: A microphone pickup pattern that has the highest sensitivity at 0° and 180° with the maximum sensitivity drop at 90° and 270°.
Figure 8 Polar Chart Example
 
Filament
Electronics: The heated element in an incandescent lamp or vacuum tube.
 
Filter
Audio, DIY, Video, Communications: A device that uses reactive components (capacitors, resistors and/or inductors) to pass and/or reject selected frequencies.
 
Filter, Active
Electronics, Audio: A filter that uses an amplifier in addition to reactive components (capacitors, resistors and/or inductors) to pass and/or reject selected frequencies.
 
Filter, Band-pass
Audio, Video, Communications: A filter that passes all frequencies within a given range (between the low cut-off frequency and the high cut-off frequency) while rejecting all frequencies below the low cut-off and above the high cut-off.
 
Filter, Band-stop
Audio, Video, Communications: A filter that rejects all frequencies within a given range (between the low cut-off frequency and the high cut-off frequency) while passing all frequencies below the low cut-off and above the high cut-off.
 
Filter, High-pass
Audio, Video, Communications: A filter that passes all frequencies above a designated cut-off frequency and rejects or attenuates all frequencies below the cut-off frequency.
 
Filter, Noise
DIY, Electronics, Plug 'n Power: A device that filters out noise generated by an electrical appliance and is attached to the offending appliance. 
 
Filter, Notch
Electronics: A filter that blocks a narrow band of frequencies and passes all frequencies above and below the band.
 
Filter, Passive
Electronics: A filter that contains only passive or non-amplifying reactive components (such as capacitors, resistors and/or inductors).
 
FIPS
Acronym: Federal Information Processing Standards
Weather: A five-digit code indicating a particular state and county. The first two digits indicate the state; the second three digits indicate the county. While some older weatheradios used FIPS codes, current models generally use SAME Codes.
 
Firewire: see IEEE-1394.
 
Firmware
Electronics: Read-only information stored within the DSP and/or microprocessor that acts as the interface between software and hardware.
 
Flash
Digital Video: A photography device that supplies additional light to compensate for low lighting, back-lighting and other lighting issues.
 
Flash Flood
Weather: A flood that rises and falls quite rapidly with little or no advance warning, usually as the result of intense rainfall over a relatively small area. Flash floods can be caused by situations such as a sudden excessive rainfall, the failure of a dam, or the thaw of an ice jam.
 
Flash Memory Card
Computers: A memory card that uses Flash RAM to store digital information such as images or audio.
 
Flash Memory Reader
Computers: An accessory that attaches to your computer by cable and allows your computer to read directly from a flash memory card.
 
Flash RAM
Acronym: Flash Random Access Memory
Computers: A rewritable memory format often used for temporary information storage.
 
Flat Bed Scanner
Digital Video: An optical scanner in which the original image remains stationary while the sensors pass over or under it.
 
Flicker
Video: A video error that occurs when the frame rate is too low, allowing the human eye to distinguish a flickering effect.
 
Flood
Weather: High water flow or an overflow of rivers or streams from their natural or artificial banks, inundating adjacent low lying areas.
 
Flood Plain
Weather: Level land that may be submerged by flood waters.
 
Flood Stage
Weather: The level of a river or stream where overflow onto surrounding areas can occur.
 
Fluorescent
Electronics: The ability to emit light when struck by electrons or other radiation.
 
Flux
DIY: The material used to remove oxide films from the surface of metals in preparation for soldering.
Electronics, Metal Detectors: The lines of force in a magnetic field.
 
FM
Acronym: Frequency Modulation
Communications: A modulation method that modulates a signal onto a carrier wave so that the frequency varies according to a characteristic of the signal. Compare to AM.
 
F-Number: see F-Stop.
 
Focal Length
Digital Video: The distance from the optical center of the lens to the image sensor when the lens is focused on infinity, usually expressed in millimeters.
 
Focal Ratio
Binoculars: A measurement equal to the focal length divided by the aperture.
 
Focus
Digital Video: The process of bringing the target into sharp focus on the image sensor.
 
Focus, Fixed
Digital Video: A lens that is preset to a given focus distance in order to provide the maximum depth of field.
 
Fog
Weather: a visible aggregate of minute water droplets suspended in the atmosphere at or near the surface of the earth, reducing horizontal visibility to less than 5/8 statute miles. It is created when the temperature and the dew point of the air have become the same, or nearly the same, and sufficient condensation nuclei are present. See also: advection fog, freezing fog, radiation fog, and sea fog.
 
Fog, Advection
Weather: fog that develops when warm moist air moves over a colder surface, cooling that air to below its dew point.
 
Fog Bank
Weather: A fairly well-defined mass of fog observed in the distance. Most commonly seen at sea, over a lake, or along coastal areas.
 
Fog Bow
Weather: A whitish semicircular arc seen opposite the sun in fog. The outer margin has a reddish tinge, its inner margin has a bluish tinge, and the middle of the band is white. An additional bow with reversed colors sometimes appears inside the first.
 
Fog, Freezing
Weather: A fog that occurs when the air temperature is below 0°C.
 
Fog, Ground
Weather: A fog that is created when radiational cooling at the earth's surface lowers the temperature of the air near the ground to or below its initial dew point. Primarily takes place at night or early morning.
 
Fog, Radiation
Weather: A fog that is created when radiational cooling at the earth's surface lowers the temperature of the air near the ground to or below its dew point. Formation is best when there is a shallow surface layer of relatively moist air beneath a drier layer, clear skies, and light surface winds. This primarily occurs during the night or early morning.
 
Fog, Sea
Weather: A type of advection fog which forms in warm moist air cooled to saturation as the air moves across cold water.
 
Follow-Me Roaming
Telephony: A feature in cellular service where the cellular system automatically forwards calls to a roaming mobile when it leaves its primary service area.
 
Foot-candle
Lighting: A measurement of light output in candela per square foot. It is generally defined as the amount of light projected onto a surface placed one foot from the standard candle.
 
Format
Computers: When used as a verb, formatting refers to preparing a type of recording media (whether hard drive, floppy disk, CDR, or other) for recording. When used as a noun, format refers to the file type. The primary format categories you will encounter are image and data. The tables below give general information on some of these format types. Please note: these tables are not intended to be all-inclusive.
Image
Format
Sub-Format and Description Bits-Per-Pixel and Color Type
BMP RGB encoded (OS/2) 1-bit, 4-bit, 8-bit color, 24-bit
RGB encoded (Windows) 1-bit, 4-bit, 8-bit color, 24-bit
RLE encoded (Windows) 4-bit, 8-bit color
CLP Clipboard bitmap (Windows) 1-bit, 4-bit, 8-bit color, 24-bit
Device-independent clipboard bitmap 1-bit, 4-bit, 8-bit color, 24-bit
CT Continuous Tone CMYK (SciTex) 24-bit
Continuous Tone CMY (SciTex) 24-bit
CUT Dr. Halo 8-bit color
DCX Multipage Paintbrush (Zsoft) 1-bit
DIB RGB encoded (OS/2) 1-bit, 4-bit, 8-bit color, 24-bit
RGB encoded (Windows) 1-bit, 4-bit, 8-bit color, 24-bit
RLE encoded (Windows) 4-bit, 8-bit color
EPS Image only (Adobe) 1-bit, 4-bit, 8-bit color, 24-bit
FPX Compressed (Kodak) 8-bit grey, 24-bit
Uncompressed (Kodak) 8-bit grey, 24-bit
GIF v. 87a Interlaced (Compuserve) 1-bit, 4-bit, 8-bit color
v. 87a Non-interlaced (Compuserve) 1-bit, 4-bit, 8-bit color
v. 89a Interlaced (Compuserve) 1-bit, 4-bit, 8-bit color
v. 89a Non-interlaced (Compuserve) 1-bit, 4-bit, 8-bit color
IFF Compressed (Electronic Arts) 1-bit, 4-bit, 8-bit color, 24-bit
Uncompressed (Electronic Arts) 1-bit, 4-bit, 8-bit color, 24-bit
IMG Old style (GEM Paint) 1-bit, 4-bit, 8-bit color
New style (GEM Paint) 1-bit, 4-bit, 8-bit color
JIF Huffman compressed 8-bit grey, 24-bit
JPG Huffman compressed 8-bit grey, 24-bit
Progressive 8-bit grey, 24-bit
KDC Kodak digital camera 24-bit
LBM Compressed (Deluxe Paint) 1-bit, 4-bit, 8-bit color
Uncompressed (Deluxe Paint) 1-bit, 4-bit, 8-bit color
MAC With header (MacPaint) 1-bit
Without header (MacPaint) 1-bit
MSP New version (MS Paint) 1-bit
Old version (MS Paint) 1-bit
PBM Portable bitmap (UNIX) 1-bit
PCD Photo-CD (Kodak) 24-bit
PCT PICT (Apple) 1-bit, 4-bit, 8-bit color, 16-bit, 24-bit, 32-bit
PCX v. 0 (Zsoft Paintbrush) 1-bit
v. 2 with palette info (Zsoft) 1-bit, 4-bit
v. 3 without palette info (Zsoft) 1-bit, 4-bit
v. 5 (Zsoft) 1-bit, 4-bit, 8-bit color, 24-bit
PGM Portable Graymap ASCII (UNIX) 8-bit grey
Portable Graymap Binary (UNIX) 8-bit grey
PIC Pictor/PC Paint 1-bit, 4-bit, 8-bit color
PNG Interlaced Portable Network Graphics 1-bit, 4-bit, 8-bit color, 16-bit, 24-bit, 32-bit
Non-interlaced Portable Network Graphics 1-bit, 4-bit, 8-bit color, 16-bit, 24-bit, 32-bit
PPM Portable Pixelmap (UNIX) 24-bit
PSD Photoshop (RGB or Indexed) 1-bit, 8-bit color, 24-bit
PSP RLE encoded (Paint Shop Pro) 1-bit, 4-bit, 8-bit color, 24-bit
LZ77 Compressed (Paint Shop Pro) 1-bit, 4-bit, 8-bit color, 24-bit
Uncompressed (Paint Shop Pro) 1-bit, 4-bit, 8-bit color, 24-bit
RAS Type 1 Modern (Sun) 1-bit, 8-bit color, 24-bit, 32-bit
RAW Unencoded pixel data 8-bit grey, 24-bit
RLE Compuserve 1-bit
Windows 4-bit, 8-bit color
SCT Continuous Tone CMYK 24-bit
Continuous Tone CMY 24-bit
TGA Uncompressed (Truevision) 8-bit grey, 8-bit color, 16-bit, 24-bit, 32-bit
Compressed (Truevision) 8-bit color, 16-bit, 24-bit, 32-bit
TIF Huffman compressed 1-bit
Uncompressed 1-bit, 4-bit, 8-bit grey, 8-bit color, 24-bit
Uncompressed CMYK 24-bit
Pack bits compressed 1-bit, 4-bit, 8-bit grey, 8-bit color, 24-bit
Pack bits compressed CMYK 24-bit
LZW compressed 1-bit, 4-bit, 8-bit grey, 8-bit color, 24-bit
LZW compressed CMYK 24-bit
Fax Group 3 compressed 1-bit
Fax Group 4 compressed 1-bit
WPG v. 5.0 (WordPerfect) 1-bit, 4-bit, 8-bit grey, 8-bit color
v. 5.1 (WordPerfect) 1-bit, 4-bit, 8-bit grey, 8-bit color
v. 6.0 (WordPerfect) 1-bit, 4-bit, 8-bit grey, 8-bit color, 24-bit
Data
Format
Shorthand for Description Programs
ASC ASCii MS-DOS text document with layout Most word processors
ANS ANSi Text document with layout Most word processors
PRN PRiNter General print-ready format Various program types
TXT TeXT Basic text document Most word processors
RTF Rich Text Format Formatted document Most word processors
DOC DOCument Formatted document Microsoft® Word®
DOT DOcument Template Word-processor template Microsoft® Word®
MCW MaCintosh Word Formatted document Microsoft® Word® for Macintosh®
PDF Portable Document Format Formatted document Adobe® Acrobat®
WPD WordPerfect Document Formatted document WordPerfect®
WPS Word ProceSsor Formatted document Microsoft® Works
WPT Word Processor Template Word-processor template Microsoft® Works
WRI WRIte Formatted document Microsoft® Write®
CSV Comma Separated Values Spreadsheet data Most spreadsheet and database programs
SLK Symbolic LinK Spreadsheet data Spreadsheet and other programs
WKS
WK1
WK3
WK4
WorKS
WorKs 1
W
orKs 3
W
orKs 4
Spreadsheet data Lotus® Works
XLS
XLM
XLC
XLT
XLW
XLW
eXceL Spreadsheet
eXceL Macro
eXceL Chart
eXceL Template
eXceL Workbook
eXceL Workspace
Spreadsheet data Microsoft® Excel®
DBF DBase File Database data dBase®
DIF Data Interchange Format Database data Lotus®
MDB Microsoft DataBase Database data Microsoft® Access
WQ1 Wordperfect Quattro 1 Database data Quattro®
HTM
HTML
HyperText Markup
HyperText Markup Language
Web-formatted document HTML editors and browsers
IQY
DQY
OQY
RQY
_QuerY Web query files Various program types
XML eXtensible Markup Language Web-formatted document XML editors and XML-capable browsers
 
Forward Bias: see Forward Voltage.
 
Forward Current: see Current, Forward.
 
Forward Resistance: see Resistance, Forward.
 
Forward Voltage: see Voltage, Forward.
 
Fp
Measurement: Pressure force.
 
FPX
Acronym: FlashPiX
Digital Video: An image format that contains a number of resolutions, each of which is broken into tiles that can be edited and displayed independently.
 
Frame
Video: One of the still pictures that make up a video.
 
Frame Grabber
Digital Video: A device that lets you capture individual frames out of a video camera or off of a video tape.
 
Frame Rate
Video: The number of frames that are shown or sent each second. A brief table of common frame rates is given below.
NTSC Frame Rate 30 frames per second
PAL Frame Rate 25 frames per second
Computer Display Frame Rate between 70 and 90 frames per second
 
Fraunhoffer Institute, The
Computer, Audio: The organization that helped to develop the MP3 standard and that licenses the corresponding source code for use in players and encoders.
 
Freeware
Computers: Free software, often written by hobbyist programmers and distributed free of charge by various methods.
 
Freezing Drizzle: see Drizzle, Freezing.
 
Freezing Point
Weather: The temperature at which a liquid solidifies under any given set of conditions. Pure water under atmospheric pressure freezes at 0°C or 32°F. It is the opposite of fusion. In oceanography, the freezing point of water is depressed with increasing salinity.
 
Freezing Precipitation: see Precipitation, Freezing.
 
Freezing Rain: see Rain, Freezing.
 
Frequency (F)
Communications, DIY, Electronics: The number of cycles per second in a waveform, measured in Hertz.
 
Frequency Band
Communications, Electronics: A particular frequency range, either those between a low and high cut-off or those used for a particular purpose.
 
Frequency, Crossover
Audio: The frequency that acts as the dividing line for a crossover, with higher frequencies separated from lower frequencies.
 
Frequency Division Multiple Access: see FDMA.
 
Frequency Domain Response: see Frequency Response
 
Frequency Hopping Spread Spectrum: see FHSS.
 
Frequency Range
Audio: When playing audio, frequency range describes how well the high and low sounds are reproduced. When recording audio, it describes the frequencies that the microphone is designed to record for the best results.
 
Frequency Response
Audio: How an audio system responds to different input frequencies at a given input voltage. Also called Frequency Domain Response.
 
Frequency Shift
Metal Detectors: A feature which suppresses the audio interference (crosstalk) between two detectors using identical transmit frequencies in close proximity.
 
Frequency Shift Keying: see FSK.
 
Frequency Step
Communications: The increment between displayed frequencies on a digitally-tuned scanner.
 
Fringing
Digital Video: A digital artifact, also called Chromatic Aberration, that appears as a white fringe on the edges of objects in the image and that is caused by the lens not focusing all wavelengths to the same plane.
 
Front
Weather: The transition zone or interface between two air masses of different densities, which usually means different temperatures. For example, the area of convergence between warm, moist air and cool, dry air. Related terms: cold front and warm front
 
Frost
Weather: The covering of ice crystals that forms by direct sublimation on exposed surfaces whose temperature is below freezing.
 
Frozen Precipitation: see.Precipitation, Frozen
 
FRS
Acronym: Family Radio Service
Communications: A radio service introduced by the FCC for non-licensed users. The term is used to describe the service, the 14 frequencies and the radios.
 
Fs
Audio: The resonance frequency of a speaker driver. The frequency at which the speaker driver's impedance peaks in free-air.
 
FSK
Acronym:Frequency Shift Keying
Communications: A method used to transmit and receive digital signals, with the ON and OFF states represented by varying the frequency.
 
F-Stop
Digital Video: A numerical designation (f/2, f 2.8, f3 etc.) that indicates the size of the aperture.
 
FTP
Acronym: File Transfer Protocol
Internet: The most basic means of directly transferring files among servers or between a server and an individual user's PC. See Protocol.
 
Fujita-Pearson Scale
Weather: A scale that classifies the severity of wind damage intensity based on the degree of destruction as it relates to the wind speed as well as path length and path width of the event. It is normally used to identify the most intense damage exhibited by a tornado. Developed by T. Theodore Fujita and Allen Pearson.
 
Full Duplex
Computers: A communication standard where data travels in both directions at the same time, using 100% of available bandwidth.
Audio: A soundcard standard that enables simultaneous recording and playback.
Telephony: A communication system that allows you to simultaneously talk into the telephone and hear the other party.
 
Full-wave Rectifier: see Rectifier, Full-wave.
 
Function Generator
DIY: A signal generator that can produce sine, square, triangle and sawtooth output waveforms.
 
Fuse
Electronics: A protective device placed in the current path that will melt or otherwise open when the current exceeds a predetermined maximum value.
 
Fuse, Blade-type
Electronics: A fuse used primarily in automotive applications. Click here for current blade-type fuses.
 
Fuse, Fast-acting: see Fuse, Fast-blow.
 
Fuse, Fast-blow
Electronics: A fuse that will open nearly instantly when exposed to a current condition higher than the fuse's rating.
 
Fuse, Slow-blow
Electronics: A fuse that can withstand a heavy current (usually up to ten times its rated value) for a small period of time before it opens.
 
Fuse, Time-delay: see Fuse, Slow-blow.
 
Fixed ID Codes
Communications: Receive ID codes that are always decoded by the radio transceiver regardless of the group selected by the group select switch.

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