The CCTV Glossary
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 Saturation (in colour).  The intensity of the colours in the active picture.  The degree by which
the eye perceives a colour as departing from a grey or white scale of the
same brightness.  A 100% saturated colour does not contain any white; adding white reduces
saturation.  In NTSC and PAL video signals, the colour 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.
SCART (or Peritel SCART). SCART stands for Syndicat Français des Constructeurs d'Appareils
Radio et Télévision.  A connector commonly found on television sets and video recorders, with
standard connections for audio, composite and component video in and out.
Scene illumination.  The average light level incident upon a monitored 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 colour with memory.  A colour
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.  Colour 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, it is
known as telemetry and is the mostcommon method of communicating between
keyboards, matrix and PTZ cameras.  It may be synchronous or asynchronous.
Serial interface.  A digital communications interface in which data are transmitted and
received sequentially along a single wire or pair of wires.  Common serialinterface 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 bi-directional
communication on a 3 wire connection, as a serial data stream.
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).  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/or sound)
will be during playback.  An S/N ratio is calculated with the logarithm of the normal signal
and the RMS value of the noise.A S/N ratio can be given for the luminance signal,
chrominance signal and audio signal.
Silicon.  The material of which modern semiconductor devices are made.
Simplex.  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 ofmultiplexer
operation where only one function can be performed at a time, e.g., either recording or
playback individually.
Single-mode fibre.  An optical glass fibre that comprises a core of very small diameter.
A typical single-mode fibre used in CCTV has a 9 µm core and a 125 µmouter diameter.
Single-mode fibre has less attenuation and therefore transmits signals atlonger distances
(easily up to 40km unrepeated).  Such fibres are normally used only with laser sources
because of their very small acceptance cone.
SIT.  Silicon Intensified Target.  A high sensitivity monochrome camera usable in bright
starlight.
Skin effect.  The tendency of high frequency alternating current to travel only on the
surface of a conductor.  The higher the frequency the greater the effect.  At high frequency,
high current the effect is overcome using bunched conductors or Litz wire (many small conductors).
Slow scan.  The transmission of a series of frozen images by means of analogue or digital signals
over limited bandwidth media, usually telephone.
Smear (or Transfer Smear).  An unwanted side effect of vertical charge transfer in a CCD chip.
It shows as vertical white (or sometimes red) stripes in parts of the image where there are
very bright highlights. In some modern chip sets smear is minimized to almost undetectable levels.
SMPTE.  Society of Motion Picture and Television Engineers.
SMPTE time code.  In video editing, time code that conforms to SMPTE standards.  It
consists of an 8-digit number specifying hours: minutes: seconds: frames.  Each number
identifies one frame on a videotape.  SMPTE time code may be of either the drop-frame
or non-drop-frame type.
Snow.  Random video noise on the display screen, often resulting from dirty VCR heads,
weak broadcast video reception or AGC amplifiers working at high gain.
S/N ratio.  See Signal-to-Noise ratio.
Spectrum.  In electromagnetics, the spectrum of a signal refers to the description of a
signal's amplitudeversus its frequency components.  In optics, spectrum refers to the various
light frequencies composing the white light which can be seen as rainbow colours, when
separated.
Spectrum analyser.  An electronic device that can show the frequency spectrum of an electric
signal, i.e. plots amplitude (vertically) against frequency (horizontal).
SPG.  Sync pulse generator.  A source of synchronization pulses.
Split-screen unit.  Equipment that simultaneously displays parts or more than one image
on a single monitor.  It usually refers to two images displayed on a single screen.
STP. Shielded Twisted Pair.
Staircase pattern.  The monochrome equivalent of colour bars.  A patterngenerated by the
TV generator, consisting of equal width luminance steps of 0, +20, +40, +60, +80, and
+100 IRE units and a constant amplitude chroma signal at colour burst phase.  Chroma
amplitude is selectable at 20 IRE units (low stairs) or 40 IRE units (high
stairs).  The staircase pattern is useful for checking linearity of luminance and chroma gain,
differential gain and differential phase and correctly setting up monitors.
Start bit.  A bit preceding the group of bits representing a character used to signal the arrival
of the character in an asynchronous transmission.
Steradian sr.  The steradian is the cone of light spreading out from the source which would
illuminate one square meter of the inner surface of a sphere of 1 m radius around the source.
Sub-carrier (SC).  Also known as SC: 4.43 MHz for PAL,  3.58 MHz for NTSC.  These are
the basic signals in all PAL and NTSC sync signals.  The actual frequencies are
4.43361875 MHz (PAL) and 3.579545 MHz (NTSC) .  Sub-carrier is usually divided down
from a primary crystalfrequency.  All othersynchronizing signals are directly divided down
from sub-carrier.
S-VHS.  Super Video Home System format in video recording.  A newer standard developed by
JVC, preservingthe backwards compatibility with the VHS format.  It offers much better recorded
horizontal resolution, for colour,up to 400 TV lines.  This is due to the colour being separated
from the luminance and use ofhigh quality video heads and better tapes.
SWG.  Standard Wire Gauge.  The Imperial equivalent of AWG.  The smaller the number the
larger the diameter of wire.
Sync.  Short for synchronization.
Sync generator (sync pulse generator, SPG).  Device that generates synchronizing pulses
needed by video source equipment to provide proper signal timing.  Pulses typically
produced by a sync generator could be sub-carrier, sync, blanking, H and V drives and colour
black.  Most commonly usedin CCTV are H and V drives.
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