Video Surveillance CCTV Glossary Terms
Select a letter to go to terms.
A.L.C. (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
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 alarm input.
A signal in which any level is represented by a directly proportional voltage;
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 device
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 parameter.
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.
B.L.C. (Back Light Compensation)
A feature of modern CCD cameras which electronically compensates for high
background lighting to give detail which would normally be silhouetted.
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 conductors.
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
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 picture.
The halation and defocusing effect that occurs around the bright areas of
the picture (highlight) whenever there is an increase in the brightness
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 output.
C Mount / CS Mount
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
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
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 "e;imager."e; Solid state cameras are
sometimes referred to as CCD cameras.
The common abbreviation for Closed Circuit Television. A private or closed
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
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 Static
E.I. (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
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 system.
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
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
One half of a frame of video (262.5 scan lines).
Field Of View
The maximum viewed image (area covered) a lens "e;sees."e; 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
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
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"e;, 1/3"e; and 1/2"e;.
A complete picture (525 scan lines). The frame consists of two fields of video
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 Ext. Sync)
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 Megabyte.
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
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.
I.R. (Infra Red)
A range of frequencies lower than visible red light used for covert surveillance
or as a low cost wireless video link.
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
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
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 126.96.36.199
Also see Static IP and Dynamic IP.
The adjustable opening (mechanical diaphragm) through which light can pass and
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
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
The part of a video signal that consists of the monochrome data.
A unit measuring the intensity of light. One foot-candle = 10 lux.
Manual Iris Lens
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 telemetry
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
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
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 lenses.
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 signal.
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 telephony.
Multiplex (Time Multiplex)
Using one carrier to send more than one signal. In video multiplexers, achieving
this by sending a
N.T.S.C. (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
P.A.L. (Phase 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
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
A device that compresses up to four video signals and simultaneously displays
the images onto one monitor.
Rack Mount (19"e; Rack)
An industrial standard housing 19"e; wide, its height is measured in units (U’s)
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
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 information present.
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
A loss of vertical sync which causes the picture to move up or down on the TV
A commonly used computer serial interface.
S.E.C.A.M. (See CCIR)
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 better.
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 "e;scuzzy"e;.) 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 viewed simultaneously.
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 monitor.
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
T.V.L. (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 TVL.
A picture condition in which horizontal lines are displaced in an irregular
A system utilizing ‘control code’ transmitters and receivers. These use the
video cable or a simple twisted pair cable to send their information.
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
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 encoding.
A cable, often screened, that consists of two conductors twisted together along
Uninterrupted 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.
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
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
The ratio of starting focal length (wide position) to the ending focal length
(telephoto position) of a zoom lens. Typically 10X.