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Glossary of Terms - S to Z:
S
Scene illumination
The density of light falling on the area to be viewed. For best
results the ratio of the lightest to the darkest areas should not
be more than a factor of two.
Screen splitter
A term usually used for a device that can combine the views from
two cameras on a single screen. Normally the camera syncs need to
be locked together.
SECAM
Sequential Couleur A Memoire (sequential colour with memory), the
French colour TV system also adopted in Russia. The basis of operation
is the sequential recording of primary colours in alternate lines.
The image format is 4:3, 625 lines, 50 Hz and 6-MHz video bandwidth
with a total 8 MHz of video channel width.
Signal to Noise Ratio (SNR)
A measurement of the noise level in a signal expressed in dB (decibels).
The higher the Signal to Noise ratio, the better the quality of
the signal.
SVHS or Super VHS
A higher quality extension of the VHS home videotape format, featuring
higher luminance and the ability to produce better copies.
S-Video
Type of video signal used in the Hi8 and SVHS videotape formats.
S-video transmits luminance and colour portions separately, using
multiple wires, thus avoiding the colour encoding process and its
inevitable loss of picture quality.
T
Telemetry
The system by which a signal is transmitted to a remote location
in order to control CCTV equipment e.g. to control pan and tilt
and zoom functions, switch on lights, move to preset positions etc.
The controller at the operating position is the transmitter and
there is a receiver at the remote location. The signal can be transmitted
along a simple `twisted pair' cable or along the same coaxial cable
that carries the video signal.
Timelapse VCR
A type of video recorder that can be set to record continuously
over long periods. This can be anything from three hours to 480
hours, achieved by the tape moving in steps and recording one frame
at a time. This means that if set to record over long periods much
information can be lost. On receipt of an alarm signal these machines
can be automatically switched to real time mode.
Touch screen control
A system by which all the camera controls are displayed on the screen
of a special monitor. To control any function simply requires the
screen to be touched at the appropriate symbol which can be to select
a camera or pan, tilt and zoom. The system is computer driven and
can include maps, diagrams etc. that are automatically displayed
according to the alarm received.
U
Underscanning
A technique generally used by some TV and video systems as a way
of ensuring that the complete image is always visible within a display
area; the opposite of overscanning.
V
VCR
Video Cassette Recorder aka video, video recorder.
Video Motion Detection
A method of detecting movement in the view of the camera by the
electronic analysis of the change in picture contrast.
W
White level
The brightest part of a video signal corresponding to approximately
1.0 Volt.
Y
Y/C Video
See S-video.
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