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Saturation (in colour).
The intensity of the colours in the active picture. The degree by
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
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
SCART (or Peritel SCART). SCART
stands for Syndicat Français des Constructeurs d'Appareils
Télévision. A connector commonly found on
sets and video recorders, with
standard connections for audio,
composite and component video in and out.
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
hardware methods of connecting
more external devices to a computer bus.
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.
A digital communications interface in which data are transmitted and
along a single wire or pair of wires. Common serialinterface
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
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
Signal-to-Noise ratio (S/N).
The S/N ratio is the ratio of noise to actual total
and it shows how much higher the
signal level is than the level of noise. It is expressed
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,
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
An optical glass fibre that comprises a core of very small diameter.
single-mode fibre used in CCTV has a 9 µm core and a 125
Single-mode fibre has less attenuation
and therefore transmits signals atlonger
(easily up to 40km unrepeated).
Such fibres are normally used only
with laser sources
because of their very small acceptance
SIT. Silicon Intensified
Target. A high sensitivity monochrome camera usable in bright
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
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
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,
video reception or AGC amplifiers working at high gain.
S/N ratio. See Signal-to-Noise
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
composing the white light which can be seen as rainbow colours, when
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.
Equipment that simultaneously displays parts or more than
on a single monitor. It usually
refers to two images displayed on a single screen.
STP. Shielded Twisted Pair.
The monochrome equivalent of colour bars. A patterngenerated by
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
The steradian is the cone of light spreading out from the source
illuminate one square meter of
the inner surface of a sphere of 1 m radius around the source.
Also known as SC: 4.43 MHz for PAL, 3.58 MHz for NTSC.
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
S-VHS. Super Video
Home System format in video recording. A newer standard developed
backwards compatibility with the VHS format. It offers much
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
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
black. Most commonly usedin
CCTV are H and V drives.