CCTV Glossary
Cascadia Video Products LLC
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Archive - Long-term off-line storage. In digital systems, pictures are generally archived onto
some form of hard disc, magnetic tape, floppy disk or DAT cartridge.
Artifacts - Undesirable elements or defects in a video picture. These may occur naturally in the
video process and must be eliminated in order to achieve a high-quality picture. The most
common are cross-color and cross-luminance.
ASCII - American Standard Code for Information Interchange. A 128-character set that includes
the upper case and lower-case English alphabet, numerals, special symbols and 32 control codes.
A 7-bit binary number represents each character. Therefore, one ASCII-encoded character can
be stored in one byte of computer memory.
Aspect ratio - This is the ratio between the width and height of a television or cinema picture
display. The present aspect ratio of the television screen is 4:3, which means four units wide by
three units high. Such aspect ratio was elected in the early days of television, when the majority
of movies were of the same format. The new, high definition television format proposes a 16:9
aspect ratio.
Aspherical lens - A lens that has an aspherical surface. It is harder and more expensive to
manufacture, but it offers certain advantages over a normal spherical lens.
Astigmatism - The uneven foreground and background blur that is in an image.
Asynchronous - Lacking synchronization. In video, a signal is asynchronous when its timing
differs from that of the system reference signal. A foreign video signal is asynchronous before a
local frame synchronizer treats it.
ATM - Asynchronous transfer mode. A transporting and switching method in which information
does not occur periodically with respect to some reference such as a frame pattern.
Attenuator - A circuit that provides reduction of the amplitude of an electrical signal without
introducing appreciable phase or frequency distortion.
ATSC - Advanced Television System Committee (think of it as a modern NTSC). An American
committee involved in creating the high definition television standards.
Attenuation - The decrease in magnitude of a wave, or a signal, as it travels through a medium or
an electric system. It is measured in decibels (dB).
Auto iris (AI) - An automatic method of varying the size of a lens aperture in response to changes
in scene illumination.
AWG - American wire gauge. A wire diameter specification based on the American standard.
The smaller the AWG number, the larger the wire diameter (see the reference table in the Camera
Power Supply section).
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