A
|
| 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 detail in shadows. |
| 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 decrease 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
|
| 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
|
| C Mount / CS Mount |
The
two industry standards for mounting a lens on a camera. The C-Mount
lens has a 17.5mm diameter. The CS-Mount lens has a 12.5mm diameter. |
| 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. |
| 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
(video or radio) with very low signal loss. |
| Composite
Video |
The
complete video signal consists 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. |
D
|
| 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 signals. |
| DC
Type Lens |
An
auto-iris lens with internal circuit which receives voltage and a
video signal from the camera to adjust the iris. |
| 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 image or picture. Digital
images can also be enhanced or processed further which can help detect
images that may normally go unnoticed. One of the better properties of
Digital Recording is that there is no replay degradation due to poor
tape quality and unlike conventional video recording methods Digital
Recording provides a clear image when paused. |
| 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. |
E
|
| 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. |
F
|
| 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. |
G
|
| 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. |
| 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. |
H
|
| 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) |
Cycles
per second. |
I
|
| 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. |
| Impedance |
The
effective resistance of an electronic circuit to an A.C. signal. |
| 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. |
| Iris |
The
adjustable opening (mechanical diaphragm) through which light can pass
and be regulated. |
L
|
| 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, towards Low will close the
iris. |
| 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. |
M
|
| 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. |
| 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. |
| Multiplex
(Time Multiplex) |
Using
one carrier to send more than one signal. In video multiplexers,
achieving this by sending a different cameras output in each
successive field or frame of a video signal, in a form that can later
be retrieved as single camera pictures. |
| MUX |
A
multiplexer. |
N
|
| 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
|
| 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. |
| 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 |
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. |
| Photocell |
Automatically
switches on the infra-red lights when light levels fall to a preset
level. |
| Pinhole
Lens |
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. |
| Pip |
Picture
in picture. |
| Pixel |
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. |
| Presets |
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. Special telemetry
equipment is required. |
Q
|
| Quad |
A
device that compresses up to four video signals and simultaneously
displays the images onto one monitor. |
R
|
| 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 light. |
| Random
Interlace |
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. |
| Range
Finder |
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. |
| Raster |
The
rectangular pattern of scanning lines upon which the picture is
produced. The illuminated face of the TV monitor without the video
information present. |
| Reflected
Light |
The
scene brightness or the light being reflected from a scene. |
| Resolution |
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. |
| Roll |
A
loss of vertical sync which causes the picture to move up or down on
the TV screen. |
| Rs232 |
A
commonly used computer serial interface. |
S
|
| 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. |
| Saturation
(Color) |
The
vividness of a color. It is directly related to the amplitude of the
chrominance signal. |
| Scanner |
A
pan only unit. |
| Scanning |
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 video surveillance
field, it is the panning or the horizontal camera motion. |
| Sensitivity |
A
camera's ability to reproduce a given scene with a given amount of
light. Usually expressed in foot-candles or lux. |
| Sensor |
A
device that indicates a change of state in response to an event or
stimulus. See Image Device. |
| Sequential
Switchers |
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. |
| Simplex
(Multiplexer) |
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. |
| Spot
Filter |
A
small insert used in a lens to increase the f-stop range of the lens. |
| Switcher |
A
device used to switch the video signals from two or more cameras on a
monitor. |
| Sync |
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
|
| 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. |
| Tearing |
A
picture condition in which horizontal lines are displaced in an
irregular manner. |
| Telemetry |
A
system utilizing ‘control code' transmitters and receivers. These
use the video cable or a simple twisted pair cable to send their
information. |
| Telephoto |
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. |
| Tilt |
The
up and down tilting movement of a camera. To elevate or depress the
vertical angle of view. |
| Time
Zone |
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. |
| Time-Lapse
VCR |
Video
recorder that can record frames with pauses between them thereby
extending the time that a standard length tape will last. |
| Triplex
(TM) |
Multiplexer
feature that gives you the ability to simultaneously view both
playback and live cameras within the same multi-screen, while still
encoding. |
| Twisted
Pair |
A
cable, often screened, that consists of two conductors twisted
together along their length. |
U
|
| 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. |
| Unterminated
(Hi-Z) |
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. |
V
|
| Varifocal
Lens |
See
Zoom Lens. Usually not motorized (manual). |
| VCR |
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. |
| Vext |
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. |
| Video
Printer |
A
device that prints a hard copy image from a video signal. |
| Visible
Light |
Wavelengths
of light visible to the human eye. |
| 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. |
W
|
| White
Light |
The
entire spectrum of visible light. |
Y
|
| Y/C |
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). |
Z
|
| Zoom |
The
ability to change the magnification of a scene. |
| Zoom
Lens |
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. |
| Zoom
Ratio |
The
ratio of starting focal length (wide position) to the ending focal
length (telephoto position) of a zoom lens. Typically 10X. |
