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 |
|
Activity
Detection
| |
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. |
|
Alarming
| |
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. |
|
Analog
| |
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. |
|
Aperture
| |
The lens opening that
controls the amount of light reaching the pickup
device (imager). |
|
Aspect
Ratio
| |
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. |
|
Aspherical
Lens
| |
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. |
|
Attenuation
| |
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 Compensation)
| |
A feature of modern
CCD cameras which electronically compensates for
high background lighting to give detail which would
normally be silhouetted. |
|
Back
Focus
| |
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. |
|
Balanced
Signal
| |
Method of transmitting
video, usually over twisted pair cable, that consists
of two equal but opposite signals being sent down
two conductors. |
|
Band
Width
| |
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. |
|
Base-Band
Video
| |
Unmodulated video
signal suitable for display on a monitor but not
a domestic TV. |
|
Black
Level
| |
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. |
|
Blooming
| |
The halation and defocusing
effect that occurs around the bright areas of the
picture (highlight) whenever there is an increase
in the brightness intensity. |
|
BNC
| |
Video connector, the
most commonly used in CCTV. |
|
Bridging
| |
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 distance. |
|
C.C.I.R.
| |
The European TV standard
625 lines 50 fields. |
|
Camera
| |
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. |
|
CATV
| |
Short for Cable Access
Television. The method for distributing RF signals
via coaxial cable rather than radiated through the
air. |
|
CCD
| |
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. |
|
CCTV
| |
The common abbreviation
for Closed Circuit Television. A private or closed
television system. |
|
CD-RW
| |
A CD-ROM that can
be written, erased, and rewritten by a CD-RW drive. |
|
Chrominance
(C)
| |
The part of the video
signal corresponding to the color information. |
|
Coaxial
Cable
| |
A type of shielded
cable capable of carrying a wide range of frequencies
with very low signal loss. |
|
Composite
Video
| |
The complete video
signal consisting of the video information, the
sync pulse and threshold reference signal. |
|
Contrast
| |
The range of light
and dark values in a picture or the ratio between
the maximum and the minimum brightness values. |
|
Crosstalk
| |
An undesired signal
that interferes with the desired signal. |
|
|
Db
(Decibel)
| |
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. |
|
Digital
| |
A signal that levels
are represented by binary numbers. These can be
kept in a store. |
|
Digital
Recording
| |
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 |
|
Distribution
Amplifier
| |
A device that accepts
a video signal and sends it out over a number of
independent outputs. |
|
Duplex
(Multiplexer)
| |
A multiplexer with
two frame stores allowing it to show multi-screen
pictures while performing time multiplex recording.
|
|
Dwell
Time
| |
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
IP. |
|
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 lenses. |
|
E.I.A.
(Electronic Industry Association)
| |
US TV standard 525
lines 60 fields. |
|
Equalization
| |
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. |
|
Facial
Capture
| |
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. |
|
Fiber
Optic
| |
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. |
|
Field
| |
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. |
|
Flange
Back
| |
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. |
|
Focal
Length
| |
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. |
|
Focus
| |
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. |
|
Format
| |
The size of the camera's
pickup device (imager). Current standard formats
are 1/4", 1/3" and 1/2". |
|
Frame
| |
A complete picture
(525 scan lines). The frame consists of two fields
of video information. |
|
F-Stop
| |
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.
|
|
Ghost
| |
A shadowy or weak
image in the received picture, offset to either
the right or to the left of the primary image. |
|
Gigabyte
(GB)
| |
1,024 megabytes or
1 billion characters of information. Also see Megabyte. |
|
Gray
Scale
| |
The number of variations
from white to gray to black. |
|
Ground
| |
An electrical connection
point that is common to either a metal chassis,
a terminal, or a ground bus. |
|
Ground
Loop
| |
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. |
|
Hardwired
| |
Method of controlling
camera points using multi-core cable. |
|
Horizontal
Resolution
| |
The maximum number
of individual picture elements that can be distinguished
in a single scanning line. |
|
Hz
(Hertz)
|
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
fast scan 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. |
|
Impedance
| |
The effective resistance
of an electronic circuit to an A.C. signal. |
|
Infrared
Illumination
| |
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. |
|
Insertion
Loss
| |
The signal strength
loss that occurs when a piece of equipment is inserted
into a line. |
|
Intensifier
| |
An electronic device
that creates an output image brighter than the input
(original) image. Optical amplifier. |
|
Interlace
| |
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. |
|
IP
Address
| |
The Internet Protocol
address; a unique numeric address such as 123.231.32.2
Also see Static IP and Dynamic IP. |
|
Iris
| |
The adjustable opening
(mechanical diaphragm) through which light can pass
and be regulated. |
|
|
Lens
| |
A transparent optical
component that converges light rays to form a two
dimensional image of that object. |
|
Level
Control
| |
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. |
|
Line
Lock
| |
To synchronize the
field sync pulses, of an AC powered camera, to the
frequency of the voltage input (line voltage). |
|
Looping
| |
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. |
|
Luminance
(Y)
| |
The part of a video
signal that consists of the monochrome data. |
|
Lux
| |
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. |
|
Matrix
Switcher
| |
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 control. |
|
MATV
| |
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. |
|
Megabyte
(MB)
| |
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. |
|
Microwave
| |
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. |
|
Modulate
| |
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. |
|
Monitor
| |
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. |
|
Monochrome
| |
Having only one color.
In television it is black and white. |
|
MPEG
| |
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 |
|
MUX
|
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. |
|
Noise
| |
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 Telephone Network)
| |
Standard phone lines
used to transmit fast scan pictures via modems. |
|
Pan
| |
Side-to-side movement
of a camera (on a horizontal axis). |
|
Passive
| |
A non powered element
of a system. |
|
Peak-To-Peak
| |
The amplitude difference
between the most positive and the most negative
excursions of a signal. |
|
Peripheral
|
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