- 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°.

-
- 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
WorKs 3
WorKs 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.
|