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F
FCC.  Federal Communications Commission (US).
FDDI.  Fibre Distributed Data Interface.
FFT.  Fast Fourier Transformation, see Fourier transformation.
Fibre optics.  A technology designed to transmit signals in the form of light. A Fibre Optic
system uses Optical Fibres.  Optical Fibre cable is noted for its properties of electrical isolation
and resistance to electrostatic and electromagnetic interference.
Field.  Refers to one-half of the TV frame that is composed of either all odd or even lines.  In
CCIR systems each field is composed of 625/2 = 312.5 lines (20ms), in EIA systems
525/2 = 262.5 lines (16.66ms).  There are 50 fields/second in CCIR/PAL, and 60 in the
EIA/NTSC TV system.
Fixed focal length lens.  A lens with a predetermined fixed focal length, a focusing  control and
a choice of iris functions.
Flash memory.  Nonvolatile, digital storage.  Flash memory has slower access than SRAM or
DRAM.
Flicker.  An annoying picture distortion, mainly related to vertical syncs and video fields
display.  Some flicker normally exists due to interlacing; more apparent in 50 Hz systems
(PAL).  Flicker shows also when static images are displayed on the screen such as
computer generated text transferred to video.  Poor digital image treatment, found in
low-quality system converters (going from PAL to NTSC and vice versa), creates an
annoying flicker on the screen.  There are several electronic methods to minimize flicker.
Flyback.  The period where the scanning beam returns to the starting point for the next scan.
F-number.  In lenses with an adjustable iris, the maximum iris opening is expressed as a ratio
(focal length of the lens)/(maximum effective diameter of aperture).  This maximum iris will
be marked on the front ring of the lens.
Focal length.  The distance between the optical centre of a lens and the principal convergent
focus point.
Focusing control.  A means of adjusting the lens to allow objects at various distances from the
camera to be sharply defined.
Foot-candle.  An illumination light unit used mostly in American CCTV terminology.  It
equals 10.76 times the illumination value in lux (1m² = 10.76 sq ft).
Fourier Transformation. Mathematical transformation of time domain functions into frequency
domain.
Frame.  (See also Field).  Refers to a composition of lines that make one TV frame.  In
CCIR/PAL TV system one frame is composed of 625 lines (2 fields of 312.5 lines), while
in EIA/NTSC TV system 1 frame is 525 lines (2 fields of 262.5 lines).  There are 25
frames/second in the CCIR/PAL and 30 frames /second in the EIA/NTSC TV system.
Frame integration  Is mis-named.  It is actually field integration and is the technique of
adding sucessive fields together to enhance an image in low light conditions.  Integration
over more than a few fields will cause motion blur to become an issue.
Frame store.  An electronic device that digitizes a TV frame (or TV field) of a video signal
and stores it in memory.  Multiplexers, fast scan transmitters, Quad displays and even
some of the latest colour cameras have built-in frame stores.
Frame switcher.  Another name for a simple multiplexer, which can record multiple cameras
on a single VCR (and play back any camera in full screen) but does not usually  have a
multiscreen image display.  Note : all cameras must be synchronized
Frame transfer (FT).  Refers to one of the principles of charge transfer in CCD chips.
The other two are interline and frame-interline transfer.
Frame-interline transfer (FIT).  Refers to one of the principles of charge transfer in CCD
chips.  It combines the principles of both frame transfer and interline transfer to give the
benefits of both, without their disadvantages.
Frequency.  The number of complete cycles of a periodic waveform that occur in a one
second period.  Usually specified in Hertz (formerly cycles per second).
Frequency modulation (FM).  The modulation of a carrier wave by varying its frequency in
accordance with amplitude variations of the modulating signal.
Front porch.  The blanking signal portion that lies between the end of the active line period
and the leading edge of line sync (horizontal sync), 1.5µs long in a CCIR/PAL system.
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