(Automatic Level Control)
On AI lenses, also known as the peak/average control. Adjusting this
control allows the auto iris circuitry to either take bright spots more
into consideration (peak), bringing out detail in bright areas, or less
into consideration (average) bringing out
A feature of the Generation 3 video multiplexer range that uses video
motion detection techniques to improve the camera update times. It also
gives a relay closure.
The ability of CCTV equipment to respond to an input signal, normally a
simple switch closure. The response varies depending on equipment type,
most common is for switcher to ‘hold’ on the camera corresponding to the
A signal in which any level is represented by a directly proportional
voltage; not digital.
Angle Of View
The maximum scene angle that can be seen through a lens.
The lens opening that controls the amount of light reaching the pickup
The ratio of the picture frame width to the picture frame height in
standard TV systems. It is 4 units horizontal over 3 units vertical.
A lens designed with a non spherical shape so that it refracts the light
passing through it to either lower the lens aperture so that it passes
more light or decreases barrel distortion on wide angle lenses.
A decrease or loss in a signal. Reduction of signal magnitude (loss)
normally measured in decibels.
Auto White Balance
Feature on color cameras whereby the camera constantly monitors the
light and adjusts its color to maintain white areas.
Automatic Frequency Control (AFC)
An electronic circuit used whereby the frequency of an oscillator is
automatically maintained within specified limits.
Automatic Gain Control (AGC)
An electronic circuit used by which the gain of a signal is
automatically adjusted as a function of its input or other specified
Automatic Iris Lens
A lens in which the aperture automatically opens or closes to maintain
proper light levels on the cameras pickup device.
Feature whereby the equipment automatically selects the correct
termination depending on whether the video output BNC is connected.
Baud rate is bits
/ seconds. It is a rate at which the data is being sent on RS-232 port.
A feature of modern CCD cameras which electronically compensates
for high background lighting to give detail which would normally be
The mechanical aligning of the imaging device with the focal
point of the lens. Most important on zoom lenses to ensure the image
stays in focus throughout the zoom range.
Method of transmitting video, usually over twisted pair cable,
that consists of two equal but opposite signals being sent down two
The frequency range of a signal. The span that the
information-bearing signal occupies or requires or the difference
between the lowest and highest frequency of a band.
Unmodulated video signal suitable for display on a monitor but
not a domestic TV.
The level of the video signal that corresponds to the maximum
limits of the black areas of the picture.
Blanking (Field And Line Flyback Blanking)
The operation of turning off the monitor display, or pick-up
device, during sync pulses to avoid thin white lines appearing on the
The halation and defocusing effect that occurs around the bright
areas of the picture (highlight) whenever there is an increase in the
is an industrial specification for wireless Personal Area Networks (PANs).
Bluetooth is an open specification for wireless short-range
communications. It transmits & receives via a short-range radio link
using a globally available frequency band (2.4 GHz ISM band). Bluetooth
provides a way to connect & exchange information between devices such
as mobile phones, Laptops, PCs, CNCs, PLCs over a secure, globally
unlicensed short-range Radio Frequency. The Bluetooth specifications are
developed & licensed by the Bluetooth Special Interest Group.
Video connector, the most commonly used in CCTV.
A term indicating that a high impedance video line is paralleled,
usually through a switch, to a source of video. A separate overall video
C Mount / CS
The two industry standards for mounting a lens on a camera. The C-Mount
lens has a 17.5mm flange back distance. The CS-Mount lens has a 12.5mm
flange back distance.
The European TV standard 625 lines 50 fields.
A device that translates light into a video image and transmits that
image to a monitor for viewing. It contains the image sensor and other
electronic circuitry to create a video signal.
Cathode Ray Tube (CRT)
The picture tube in a video monitor that can reproduce the picture image
seen by the camera.
Short for Cable Access Television. The method for distributing RF
signals via coaxial cable rather than radiated through the air.
Charged Coupled Device. This is a solid state semiconductor imaging
device often referred to as an integrated circuit, chip or "imager."
Solid state cameras are sometimes referred to as CCD cameras.
The common abbreviation for Closed Circuit Television. A private or
closed television system.
A CD-ROM that can be written, erased, and rewritten by a CD-RW drive.
The part of the video signal corresponding to the color information.
A type of shielded cable capable of carrying a wide range of frequencies
with very low signal loss.
The complete video signal consisting of the video information, the sync
pulse and threshold reference signal.
The range of light and dark values in a picture or the ratio between the
maximum and the minimum brightness values.
An undesired signal that interferes with the desired signal.
A measure of the power ratio of two signals. It is equal to ten times
the logarithm of the ratio of the two the iris.
DC Type Lens
An auto-iris lens with internal circuit which receives voltage and a
video signal from the camera to adjust signals.
Depth Of Field
The area in focus in front of and behind the subject.
A signal that levels are represented by binary numbers. These can be
kept in a store.
This is the latest form of recording and is relatively new to the CCTV
industry as a result is not the most economical method however it does
have several advantages over the VCR analogue tape recorders. First of
all it enables quick access to the desired
A device that accepts a video signal and sends it out over a number of
A multiplexer with two frame stores allowing it to show multi-screen
pictures while performing time multiplex recording.
The length of time a switcher displays one camera before sequencing to
the next. Usually a variable setting.
Dynamic IP Address
A Dynamic IP address is a type of account from an ISP (internet service
provider) where your computer or network is assigned an IP address that
constantly changing and never remains the same. Also see IP Address and
(Electronic Iris) Shutter
Electronic Iris shuttering is the ability of the camera to compensate
for moderate light changes in indoor applications without the use of
auto iris lenses.
E.I.A. (Electronic Industry Association)
US TV standard 525 lines 60 fields.
The process of correcting losses of certain components in a signal.
Ext. Sync (External Sync)
The ability of CCTV equipment, normally cameras, to accept one or more
of the standard sync formats so as to align itself to the rest of the
Corner mounted cameras are very effective at capturing overview scene
surveillance. In order to obtain facial capture surveillance for
positive identification purposes, cameras should be mounted at vertical
height conducive for facial capture (for example, in light switches).
Lenses selected should produce identification level imaging, ie no less
than 120% vertical image of the person.
The process of transmitting light through a long, flexible fiber such as
glass or plastic, for the purpose of transmitting video, audio, or data
over long distances.
One half of a frame of video (262.5 scan lines).
Field Of View
The maximum viewed image (area covered) a lens "sees." The horizontal or
vertical scene size at a given distance from the camera.
The distance from the flange of the lens (beginning of the lens mount)
to the focal plane. C-mount lenses have a flange back distance of
17.526mm vs. 12.5mm for CS-mount.
The distance (in millimeters) from the lens to the surface of the image
sensor. The shorter the distance, the wider the view; the longer the
distance, the narrower (telephoto) the view.
The focal point. An adjustment to the lens optics to improve the clarity
of the picture.
Foot Candle (FC)
A measurement of light. 1 lumen per square foot.
The size of the cameras pickup device (imager). Current standard formats
are 1/4", 1/3" and 1/2".
A complete picture (525 scan lines). The frame consists of two fields of
A term used to indicate the speed of a lens. The smaller the f-number,
the greater is the amount of light passing through the lens
Gen. Lock (See
To synchronize one piece of equipment to the sync pulses of another.
A shadowy or weak image in the received picture, offset to either the
right or to the left of the primary image.
1,024 megabytes or 1 billion characters of information. Also see
The number of variations from white to gray to black.
An electrical connection point that is common to either a metal chassis,
a terminal, or a ground bus.
Effects video pictures in the form of a black shadow bar across the
screen or as tearing in the top corner of a picture. Caused by different
earth potentials in a system.
known as MPEG4 AVC, The standard is expected to offer up to twice the
compression of the current MPEG4 ASP (Advanced Simple Profile), in
addition to improvements in perceptual quality. The H.264 standard can
provide DVD-quality video at under 1 Mbps, and is considered promising
for full-motion video over wireless, satellite, and ADSL Internet
Method of controlling camera points using multi-core cable.
The maximum number of individual picture elements that can be
distinguished in a single scanning line.
Cycles per second.
IEEE 802.11 is a set of standards for
Wireless Local Area Network (WLAN) computer communication, developed
by the IEEE LAN / MAN Standards Committee (IEE 802) in the 5 GHz and
2.4 GHz public spectrum bands. Although the terms 802.11 & Wi-Fi are
often used interchangeably, the Wi-Fi Alliance uses the term "Wi-Fi"
to define a slightly different set of overlapping standards. In some
cases, market demand has led the Wi-Fi Alliance to begin certifying
products before amendments to the 802.11 standard are complete.
A range of frequencies lower than visible red light used for covert
surveillance or as a low cost wireless video link. Measured in nano
meters. 850nm is visible to the human eye. It has a red glow. 940nm is
not visible to human eye, only the camera can see.
I.S.D.N. (Integrated Services Digital Network)
Digital phone lines from which allow transmission of video signals via
fastscan at speeds of 128Kb/second; used with terminal adapters.
Image Burn (Retained Image)
A change produced in or on the target of the pickup device which remains
after the removal of a previously stationary light image.
Image Device (Imager)
The detector in the camera, either a tube or a CCD solid state device.
The effective resistance of an electronic circuit to an A.C. signal.
When a “low-light” is subject to dark conditions, active infrared
illumination must be applied for best results. Active infrared
illumination is a new surveillance technology that is so effective that
the images produced are often mistaken for regular daytime monochrome
images. Active infrared illumination is a cost-effective technology for
enabling truly effective 24/7 surveillance in any lighting conditions
including total darkness.
The signal strength loss that occurs when a piece of equipment is
inserted into a line.
An electronic device that creates an output image brighter than the
input (original) image. Optical amplifier.
A scanning process where every other horizontal line is scanned in one
field while the alternate lines are scanned in the next field to produce
a complete picture frame.
Internal Sync (Crystal Controlled)
A camera that generates its sync pulses without reference to any other
source. Normally using a crystal controlled oscillator.
The Internet Protocol address; a unique numeric address such as
18.104.22.168 Also see Static IP and Dynamic IP.
The adjustable opening (mechanical diaphragm) through which light can
pass and be regulated.
A digital image format commonly used in digital recording, for storing
high-quality color and grayscale photographs in compressed bitmap form.
A transparent optical component that converges light rays to form a two
dimensional image of that object.
Main iris control. Used to set the auto-iris circuit to a video level
desired by the user. After set-up, the circuit will adjust the iris to
maintain this video level in changing lighting conditions. Turning the
control towards High will open the iris, to
License Plate Reading
License plate reading requires specialized equipment in order to
successfully overcome the challenges related to speed, lighting,
reflectivity and headlight glare. Cameras chosen should be designed
specifically for license plate reading as most conventional cameras will
not work on a consistent basis. Infrared lighting is typically required
for performance during both day and night.
Line Amplifier (Video Line Corrector)
A device to make good the loss of signal strength and quality due to
long cable runs.
To synchronize the field sync pulses, of an AC powered camera, to the
frequency of the voltage input (line voltage).
A term indicating that a high impedance device has been permanently
connected in a parallel to a video source. Individual balanced video
outputs for each video input.
The part of a video signal that consists of the monochrome data.
A unit measuring the intensity of light. One foot-candle = 10 lux.
A lens with a manual adjustment to set the iris opening (F stop) in a
fixed position. Generally used for fixed lighting applications.
A switcher able to route any of its camera inputs to any of its monitor
outputs; a name usually reserved for large systems, that often includes
Short for Multiple Access Television. The method for distributing RF TV
signals by broadcasting them through the air.
Mechanical Focus (Back-Focus, Racking)
The mechanical aligning of the imaging device with the focal point of
the lens; most important on zoom lenses to ensure the image stays in
focus throughout the zoom range.
1,048,576 bytes or 1,024 kilobytes. Used to measure computer memory.
Sometimes used to mean 1 million bytes or 1,024,000 bytes (1,000
kilobytes). Also see Gigabyte.
Radio frequencies between 1 - 30 GHz used for video transmission over
Minimum Object Distance (M.O.D.)
The closest distance a given lens will be able to focus upon an object.
This is measured from the vertex (front) of the lens to the object. Wide
angle lenses generally have a smaller M.O.D. than large focal length
To change or vary some parameter such as varying the amplitude of a
signal for amplitude modulation or the frequency of a signal for
frequency modulation. A modulator is the circuit that modulates the
A device that converts electronic signals into the video image that was
generated by the camera and lens. The picture end of a CCTV system.
Having only one color. In television it is black and white.
MPEG is a video compression method commonly used in digital recording.
MPEG-1 is a standard for CD-ROM video and audio. MPEG-2 is a standard
for full-screen, broadcast quality video.MPEG-4 is a standard for video
Multiplex (Time Multiplex)
Using one carrier to send more than one signal. In video multiplexers,
achieving this by sending a
(National Television Standards Committee. See E.I.A.)
Color TV system used in the USA. CCTV
N/D (Neutral Density)
A filter that attenuates light equally over the whole visible spectrum.
Undesired signal(s) that corrupts the original video signal and may
reduce image quality.
Alternate Line. See CCIR)
Color TV system used in the UK
P.S.T.N. (Public Switched Telephone Network)
Standard phone lines used to transmit fastscan pictures via modems.
Side-to-side movement of a camera (on a horizontal axis).
A non powered element of a system.
The amplitude difference between the most positive and the most negative
excursions of a signal.
An optional device that can enhance a CCTV system, for example, a
multiplexer, VCR, photo printer, etc.
Phase Adjustable (See Line Lock)
The ability to delay the line locking process, so as to align cameras
fed from A.C. voltages on different phases.
Automatically switches on the infra-red lights when light levels fall to
a preset level.
Lens used for applications where the camera/lens must be hidden. Front
of lens has a small opening to allow the lens to view an entire room
through a small hole in a wall.
Picture in picture.
Picture element. The smallest cell or area of a CCD chip capable of
displaying detail on a screen. The greater the number of pixels, the
higher the resolution.
The pre-positioning of pan, tilt and zoom cameras by the use of
potentiometers in the moving parts of the camera head. These allow the
control equipment to store and move to a set reference point when the
controller dictates or when an alarm exists.
A device that compresses up to four video signals and simultaneously
displays the images onto one monitor.
Rack Mount (19"
An industrial standard housing 19" wide, its height is measured in units
(U’s) of 1.75".
Radio Frequency (R.F.)
Signals with a repetition rate above audible range, but below the
frequencies associated 4 With heat and light.
Redundant Arrays of Independent Disks. The use of two or more disk
drives instead of one disk, which provides better disk performance,
error recovery, and fault tolerance, and includes interleaved storage
techniques and mirroring of important data.
A scanning technique commonly used in CCTV systems in which there is no
external control over the scanning process. That is, there is no fixed
relationship between adjacent lines and successive fields.
Used to determine the focal length needed and what the picture will look
like on the monitor. The user looks through the device and adjusts the
range finder to the desired picture. Numbers on the outside of the range
finder indicate the focal length neede
The rectangular pattern of scanning lines upon which the picture is
produced. The illuminated face of the TV monitor without the video
The scene brightness or the light being reflected from a scene.
A measure of the ability of a camera or television system to reproduce
detail. Typically refers to the number of picture elements that can be
reproduced with good definition.
A loss of vertical sync which causes the picture to move up or down on
the TV screen.
A commonly used computer serial interface. It is a universal
serial port for data transfer. In telecommunications, RS-232
(Recommended Standard 232) is a standard for serial binary data signals
connecting between a DTE (Data Terminal Equipment) and a
DCE (Data Circuit Termination Equipment). It is commonly used in
computers & Data collection devices. A similar ITU-T standard is called
Color TV system used in France.
S.V.H.S. (Super Video Home System)
New format high resolution VHS video recorders, capable of giving
greatly improved picture if all features are used. VHS compatible.
S/N Ratio (Signal To Noise Ratio)
Measure of noise levels of a video signal; the higher the number the
The vividness of a color. It is directly related to the amplitude of the
A pan only unit.
The rapid movement of the election beam in a pickup device of a camera
or in the CRT of a television receiver. It is formatted in a
line-for-line manner across the photo sensitive surface which produces
or reproduces the video picture. When referred to a
Small Computer Systems Interface (Pronounced "scuzzy".) A ultra
high-speed interface that can connect to computer devices such as a hard
drive or CD-Rom. A SCSI channel can connect up to seven devices.
A cameras ability to reproduce a given scene with a given amount of
light. Usually expressed in foot-candles or lux.
A device that indicates a change of state in response to an event or
stimulus. See Image Device.
Are commonly used devices in small to medium sized CCTV systems. The
sequential switcher alternates the displayed video image from one camera
to the next. However, with sequential switching not all cameras can be
A multiplexer with 1 frame store that can either time multiplex records
or show multi-screen pictures in live or play back. It cannot record the
multiplexer pictures whilst showing multi-screen pictures.
Solving Focus Shift
Filtering techniques can be applied to solve the problem of focus shift
under active infrared lighting. Cameras behave differently under visible
light and infrared light, with one of the chief differences being focal
properties. Day-night mechanical filters solve this problem by blocking
IR light from during the day and optimizing IR response during the
night. The result is a sharply focused image in day and dark conditions.
A small insert used in a lens to increase the f-stop range of the lens.
Static IP Address
A Static or Dedicated IP address is a type of account from an ISP where
your computer or network is assigned the same constant IP Address at all
times. Also see IP Address and Dynamic IP.
A device used to switch the video signals from two or more cameras on a
Super HAD CCD
Super HAD (Hole Accumulation Diode) CCDs allow more light to pass to
each pixel, increasing sensitivity and reducing noise.
Abbreviation for synchronization. Electronic pulses that are inserted in
to video signal for the purpose of assembling the picture information in
the correct position.
(Television Lines - Resolution)
The maximum number of changes between light and dark on a picture across
3/4 of the width dictates the resolution of a CCTV product, measured in
A picture condition in which horizontal lines are displaced in an
A system utilizing ‘control code’ transmitters and receivers. These use
the video cable or a simple twisted pair cable to send their
A lens used to produce a larger image of a distant object.
Terminated (75 Ohm Terminated)
Video input of a piece of CCTV equipment, wired to be the last in a
particular video line.
The up and down tilting movement of a camera. To elevate or depress the
vertical angle of view.
Time intervals during which an activity is permitted.
Timebase Corrector (T.B.C.)
Electronic circuit that aligns unsynchronized video signals before
signal processing. Used in multiplexers and quad splitters.
Video recorder that can record frames with pauses between them thereby
extending the time that a standard length tape will last.
Multiplexer feature that gives you the ability to simultaneously view
both playback and live cameras within the same multi-screen, while still
A cable, often screened, that consists of two conductors twisted
together along their length
Power Supply (Ups)
Equipment that supplies power to a system in the event the primary power
is lost. It may consist of batteries or auxiliary motor generators.
Video input of a piece of CCTV equipment, wired so as to allow the video
signal to be fed to further equipment. Does not necessarily include
extra sockets for the extra coaxial cables.
See Zoom Lens. Usually not motorized (manual).
A device that records video images on tape.
Vertical Interval Switching
Sequential switchers waiting until the current field has finished before
they display the next camera, even though the dwell time has elapsed.
A multiplexer feature that uses a pulse generated by the VCR so that the
multiplexer automatically adjusts to the VCR time lapse speed.
Video Motion Detection (V.M.D.)
A system that uses the video signal from a camera to determine if there
is any movement in the picture and set of an alarm.
A device that prints a hard copy image from a video signal.
Video Type Lens
An auto-iris lens without an internal circuit to control the iris. All
iris control voltages come from a circuit located within the camera.
Wavelengths of light visible to the human eye.
Wi-Fi is a wireless technology brand
owned by the Wi - Fi Alliance intended to improve the interoperability
of wireless Local Area Network products based on the IEEE 802.11
standards. Common applications for Wi-Fi include internet & VoIP phone
access, and network connectivity. The Wi-Fi Alliance is a consortium of
separate & independent companies agreeing to a set of common
interoperable products based on the family of IEE 802.11 standards. The
Wi-Fi Alliance certifies products via a set of established test
procedures to establish interoperability. Those manufacturers that are
members of Wi-Fi Alliance whose products pass these interoperability
tests can mark their products and product packaging with the Wi-Fi logo.
A digital file commonly used in digital recording, which contains a
representation of sound waves in digital form; limited in duration and
The entire spectrum of visible light.
A method of sending video pictures in 2 separate parts down 2 separate
cables. The component parts are Y (the Black and White portion) and C (
the color portion).
The ability to change the magnification of a scene.
A lens with a variable focal length. This lens may be effectively used
as a wide angle, standard, or telephoto lens by varying the focal length
of the lens. A varifocal lens.
The ratio of starting focal length (wide position) to the ending focal
length (telephoto position) of a zoom lens. Typically 10X.