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 detail in
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 alarm input.
A signal in which any level
is represented by a directly proportional voltage; not
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
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 camera's pickup device.
Auto-Terminating Feature whereby the equipment automatically
selects the correct termination depending on whether the
video output BNC is connected.
B.L.C. (Back Light
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.
signal suitable for display on a monitor but not a domestic
The level of the video signal
that corresponds to the maximum limits of the black areas of
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
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 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
The picture tube in a video
monitor that can reproduce the picture image seen by the
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
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
A device that accepts a video
signal and sends it out over a number of independent
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
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 IP.
Electronic Iris shuttering is
the ability of the camera to compensate for moderate light
changes in indoor applications without the use of auto iris
US TV standard 525 lines 60
The process of correcting
losses of certain components in a signal.
Ext. Sync (External
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
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
Foot Candle (FC)
A measurement of light. 1
lumen per square foot.
The size of the camera's
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 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.
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 a system.
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.
Services Digital Network)
Digital phone lines from
which allow transmission of video signals via fast scan at
speeds of 128Kb/second; used with terminal adapters.
Image Burn (Retained
A change produced in or on
the target of the pickup device which remains after the
removal of a previously stationary light image.
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
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.
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 188.8.131.52 Also
see Static IP and Dynamic IP.
The adjustable opening
(mechanical diaphragm) through which light can pass and be
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, too
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.
(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.
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
Short for Multiple Access
Television. The method for distributing RF TV signals by
broadcasting them through the air.
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 medium/long distance.
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.
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.
P.A.L. (Phase Alternate
Line. See CCIR)
Color TV system used in the UK
P.S.T.N. (Public Switched
Standard phone lines used to transmit
fast scan pictures via modems.
Side-to-side movement of a camera (on a
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
The ability to delay the line locking
process, so as to align cameras fed from A.C. voltages on
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
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" Rack)
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
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 needed.
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 good
A loss of vertical sync which causes the
picture to move up or down on the TV screen.
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
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
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 chrominance signal.
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
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 camera's 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
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
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 correct position.
T.V.L. (Television Lines
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 manner.
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
Terminated (75 Ohm
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
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 their length.
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
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
A digital file commonly used in digital
recording, which contains a representation of sound waves in
digital form; limited in duration and frequency.
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.
ratio of starting focal length (wide position) to the ending
focal length (telephoto position) of a zoom lens. Typically 10X.