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CCTV Glossary

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Saturation (in color). - The intensity of the colors in the active picture. The degree by which the

eye perceives a color as departing from a gray or white scale of the same brightness. A 100%

saturated color does not contain any white; adding white reduces saturation. In NTSC and PAL

video signals, the color saturation at any particular instant in the picture is conveyed by the

corresponding instantaneous amplitude of the active video sub-carrier.

Scanning. - The rapid movement of the electron beam in the CRT of a monitor or television

receiver. It is formatted line-for-line across the photo-sensitive surface to produce or reproduce the

video picture. When referred to a PTZ camera, it is the panning or the horizontal camera motion.

Scanner. - 1. When referring to a CCTV device it is the pan only head.

2. When referring to an imaging device it is the device with CCD chip that scans

documents and images.

Scene illumination. - The average light level incident upon a protected area. Normally measured

for the visible spectrum with a light meter having a spectral response corresponding closely to that

of the human eye and is quoted in lux.

Scotopic vision. - Illumination levels below 10–2 lux, thus invisible to the human eye.

SCSI. - Small computer systems interface. A computer standard that defines the software and

hardware methods of connecting more external devices to a computer bus.

SECAM. - Sequential Couleur Avec Memoire, sequential color with memory. A color television

system with 625 lines per frame (used to be 819) and 50 fields per second developed by France

and the former U.S.S.R. Color difference information is transmitted sequentially on alternate lines

as an FM signal.

Serial data. - Time-sequential transmission of data along a single wire. In CCTV, the most

common method of communicating between keyboards and the matrix switcher and also

controlling PTZ cameras.

Serial interface. - A digital communications interface in which data are transmitted and received

sequentially along a single wire or pair of wires. Common serial interface standards are RS-232

and RS-422.

Serial port. - A computer I/O (input/output) port through which the computer communicates with

the external world. The standard serial port is RS-232 based and allows bidirectional

communication on a relatively simple wire connection as data flow serially.

Sidebands. The frequency bands on both sides of a carrier within which the energy produced by

the process of modulation is carried.

Signal-to-Noise ratio (S/N). - An S/N ratio can be given for the luminance signal, chrominance

signal and audio signal. The S/N ratio is the ratio of noise to actual total signal, and it shows how

much higher the signal level is than the level of noise. It is expressed in decibels (dB), and the

bigger the value is, the crisper and clearer the picture and sound will be during playback. An S/N

ratio is calculated with the logarithm of the normal signal and the noise RMS value.

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Cascadia Digital video recorder Manual do Utilizador Página 32