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video mapping A system of surveillance or mapping
in which, for reference, the outlines of the
area being surveyed are superimposed electronically
on the radar display of the area.
video masking A form of radar signal processing
in which ground clutter and other unwanted
echoes are removed, making the desired targets
more readily visible.
video mixer A circuit or device for mixing the signals
from two or more television cameras.
video modulation In television transmission, amplitude
modulation of the carrier wave with
pulses and waves corresponding to the picture elements.
video on demand Television service in which subscribers
can choose the programs they want to
watch, and also the specific times for viewing.
video random-access memory Abbreviation,
VRAM. In computer systems, RANDOM-ACCESS
MEMORY used primarily for enhancing the performance
of the display.
video recording 1. Recording wideband material
(such as a video signal) on a tape or disc. 2. The
recording made of a telecast. Also see VIDEO-
TAPE RECORDER.
video signal 1. In television, the amplitude-modulated
signal containing picture information and
pulses. Also see VIDEO, 2 and VIDEO MODULA-
TION. 2. Broadly, a telecast signal, including
sound.
Whitest
signal Black
Dark
Grey White
grey
} Blacker-than-black
region
videotape recording 1. Abbreviation, VTR. The
technique of recording video signals on magnetic
tape. Also see VIDEO RECORDING, 1, 2 and
VIDEOTAPE. 2. A tape on which a video signal
has been recorded.
videotext A system that allows television viewers
to dial up special material, such as stock market
quotations, weather data, sports scores, etc.
vidicon A television camera tube in which the electron
beam scans a charged-density pattern that
has been formed and stored on the surface of the
photoconductor. It is commonly used in camcorders,
closed-circuit television systems, and
robot vision systems. Its assets include compactness
and sensitivity.
viewfinder An accessory or integral device in
which an image (formed optically or electronically)
corresponds to the image viewed by the
camera with which it is used.
viewing mesh In a cathode-ray storage tube, the
mesh on which the image is presented for viewing
by the operator. Also see CHARGE-STORAGE
TUBE.
viewing mirror In an oscilloscope-camera assembly,
a flat, slant-mounted mirror that reflects the image
on the oscilloscope screen to the viewer’s eye.
viewing screen In a cathode-ray device, such as
an oscilloscope tube or television picture tube,
the face on which the image appears.
viewing time In a storage type cathode-ray tube,
the length of time for which the image persists.
viewing window See WINDOW, 2.
Villard circuit 1. A voltage-doubler circuit using
only one diode and two capacitors. The opencircuit
direct-current output voltage is approximately
twice the peak value of the
alternating-current input voltage. Also see VOL-
TAGE DOUBLER. 2. See SELECTOJECT.
Zero signal
C1
video signal
ac
Input E rms
D
E dc
+ dc
Output
_
video stretching In some electronic navigation
systems, increasing the duration of a video pulse.
video synthesizer A computerized device that produces
graphical renditions of objects or circuits
in three dimensions.
videotape 1. A special magnetic tape for video
recording (see VIDEO RECORDING, 2). 2. To
make a video recording.
videotape recorder Abbreviation, VTR. A wideband,
magnetic-tape recorder for producing video
recordings with a camera, or for making a record
of television programs, for subsequent reproduction
(playback).
C2
E dc = 2.82 E rms
Villard circuit, 1
Villari effect In certain magnetostrictive materials,
the change in magnetic induction that accompanies
the application of a mechanical stress in a
given direction. Also see MAGNETOSTRICTION.
vinyl A general name for vinyl copolymer resins.