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- S/N ratio
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Stands for Signal to Noise ratio. This is calculated with the logarithm of the normal signal and the noise RMS value.
- Scene illumination
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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
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Scotopic Vision levels are illumination levels below 10^-2 lux, thus invisible to the human eye.
- Silicon
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The raw material of which modern semiconductor devices are made.
- Simplex
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In general, it refers to a communications system that can transmit information in one direction only. In CCTV, simplex is used to describe a method of multiplexer operation where only one function can be performed at a time, eg. either recording or playback individually.
- Skin effect
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The tendency of alternating current to travel only on the surface of a conductor as its frequency increases.
- Slow scan
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The transmission of a series of frozen images by means of analog or digital signals over limited bandwidth media, usually telephone.
- Smear
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An unwanted side-effect of vertical charge transfer in a CCD chip. It shows vertical bright stripes in places of the image where there are very bright areas. In better cameras smear is minimised to almost undetectable levels.
- SMPTE
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Society of Motion Picture and Television Engineers.
- Spectrum analyser
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An electronic device that can show the spectrum of an electric signal.
- Spectrum
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In Electromagnetics, spectrum refers to the description of a signal's amplitude versus its frequency components. In optics, spectrum refers to the light frequencies composing the "white light" which can be seen as rainbow colours.
- SPG
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Stands for Sync Pulse Generator. A source of synchronisation pulses.
- Split Screen Unit (Quad compressor)
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Equipment which simultaneously displays parts or more than one image on a single monitor. It usually refers to four quadrants display.
- S-VHS
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Super VHS format of video recording. A newer standard proposed by JVC, preserving the downards compatibility with the VHS format. It offers much better horizontal resolution up to 400 TV lines. This is mainly due to the colour separation techniques, high quality video heads and better tapes.
- Sync
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This is short from synchronisation pulse.
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