Glossary Of Terms (S - Z) - CCTV

S/N RATIOuseful in CCTV, such as external alarm trigger, time
Signal-to-Noise ratio is calculated with the logarithm ofand date superimposed on the video signal, alarm
the normal signal and the noise RMS value.search and so on.
SCENE ILLUMINATIONTIME LAPSE VIDEO RECORDING
The average light level incident upon a protected area.The intermittent recording of video signals at intervals
Normally measured for the visible spectrum with a lightto extend the recording time of the recording medium.
meter having a spectral response correspondingIt is usually measured in reference to a 3 hr (180 min)
closely to that of the human eye and is quoted in lux.tape.
Scotopic Vision levels are illumination levels below 10-2TIME MULTIPLEXING
lux, thus invisible to the human eye. Silicon. The rawThe technique of recording several cameras onto,
material of which modern semiconductor devices areusually, one time lapse VCR by sequentially sending
made.camera pictures with a timed interval delay to match
SIMPLEXthe time lapse mode selected on the recorder.
In general, it refers to a communications system thatUHF SIGNAL
can transmit information in one direction only. In CCTV,Ultra high frequency signal. In television it is defined to
simplex is used to describe a method of multiplexerbelong in the radio spectrum between 470 MHz and
operation where only one function can be performed850 MHz. Unbalanced signal. In CCTV, this refers to a
at a time, eg. either recording or playback individually.type of video signal transmission through a coaxial
SKIN EFFECTcable. It is called unbalanced because the signal travels
The tendency of alternating current to travel only onthrough the centre core only, while the cable shield is
the surface of a conductor as its frequency increases.used for equating the two voltage potentials between
SLOW SCANthe coaxial cable ends.
The transmission of a series of frozen images byUPS
means of analog or digital signals over limitedUninterruptible power supply. These are power supplies
bandwidth media, usually telephone.used in the majority of high security systems, whose
SMEARpurpose is to back-up the system for at least 10
An unwanted side effect of vertical charge transfer inminutes without mains power. The duration of this
a CCD chip. It shows vertical bright stripes in places ofdepends on the size of the UPS, usually expressed in
the image where there are very bright areas. In betterVA, and the current consumption of the system itself.
cameras smear is minimised to almost undetectableVDA
levels.Video Distribution Amplifier. A device that provides
SMPTEmultiple outputs from one video signal such that
Society of Motion Picture and Television Engineers.interference to one output will not affect others.
Spectrum analyser. An electronic device that canshowVERTICAL SHIFT REGISTER
the spectrum of an electric signal.The mechanism in CCD technology whereby charge is
SPECTRUMread out from the photo sensors of an Interline
In Electromagnetics, spectrum refers to the descriptionTransfer or Frame Interline Transfer sensor.
of a signal's amplitude versus its frequencyVHF
components. In optics, spectrum refers to the lightStands for Very High Frequency. A signal
frequencies composing the "white light" which can beencompassing frequencies between 30 and 300 MHz.
seen as rainbow colours.In television, VHF Band I uses frequencies between 45
SPGMHz and 67 MHz, and between 180 MHz and 215
Stands for Sync Pulse Generator. A source ofMHz for Band III. Band II is reserved for FM radio from
synchronisation pulses.88 MHz to 108 MHz.
SPLIT SCREEN UNITVHS
(Quad compressor). Equipment which simultaneouslyStands for Video Home System, as proposed by JVC,
displays parts or more than one image on a singlea video recording format that is most often used in
monitor. It usually refers to four quadrants display.homes, but also in CCTV. It has its own limitations due
S-VHSto the concept itself, the speed of recording, the
Super VHS format of video recording. A newermagnetic tapes used and the colour separation
standard proposed by JVC, preserving the downwardtechnique. Most of the CCTV equipment today
compatibility with the VHS format. It offers muchsupersedes VHS resolution.
better horizontal resolution up to 400 TV lines. This isVIDEO EQUALISATION CORRECTOR
mainly due to the colour separation techniques, high(Video Equaliser). A device which corrects for unequal
quality video heads and better tapes. Sync. This isfrequency losses and/or phase errors in the
short from synchronisation pulse.transmission of a video signal. Video frame store. A
TBCdevice which enables digital storage of one or more
Time Base Correction. Refers to the synchronisationimages for steady display on a video monitor.
of various signals inside a device such as a multiplexerVIDEO IN-LINE AMPLIFIER
or a TBC Corrector.A device providing amplification of a video signal.
TDGVIDEO MATRIX SWITCHER
Short for time and date generator.(VMS). A device for switching more than one camera,
TELEMETRYVCR, video printer and similar, to more than one
Remote controlling system of, usually, digital encodedmonitor, VCR, video printer and similar. Much more
data, intended to control pan, tilt, zoom, focus, presetcomplex and more powerful than video switchers.
positions, wash, wipe and similar. Being digital, it isVIDEO MONITOR
usually sent via twisted pair cable, or coaxial cableA device for converting a video signal into an image.
together with the video signal.VIDEO MONITOR
TERMINATIONA device for converting a video signal into an image.
This usually refers to the physical act of terminating aVIDEO PRINTER
cable with a special connector, which for coaxial cableA device for converting a video signal to a hard copy
is, usually, BNC. For fibre optic cable this is the STprintout. It could be a monochrome (B/W) or colour.
connector. It can also refer to the impedance matchingThey come in different format sizes. Special paper is
when electrical transmission is in use. This is especiallyneeded.
important for high frequency signals, such as the videoVIDEO SIGNAL
signal, where the characteristic impedance is acceptedAn electrical signal containing all of the elements of the
to be 75 Ohms.image produced by a camera or any other source of
TIME LAPSE VCRvideo information.
(TL VCR). A video recorder, most often in VHSVIDEO SWITCHER
format, that can prolong the video recording on a singleA device for switching more than one camera to one
tape up to 960 hours (this refers to a 180 min tape).or more monitors manually, automatically or upon
This type of VCRs are very often used in CCTVreceipt of an alarm condition.
systems. The principle of operation is very simpleVITS
– instead of having the video tape travel at aVideo Insertion Test Signals. Special shaped electronic
constant speed of 2.275 cm/s (which is the case withsignals inserted in the "invisible" lines (in the case of
the domestic models of VHS VCRs), it moves withPAL, lines 17, 18, 330 and 331) that are used to
discrete steps which can be controlled. Time Lapsedetermine the quality of reception.
VCRs have a number of other special functions very