| • AC Power |
Alternating Current Power. In the United States, the standard AC Power
is single-phase 117VAC/60Hz and is provided from power outlets in the house.
24V AC power can be produced from an AC Adapter. |
| • Alarm Sensor |
Like Video Motion Detector, detects changes of motion to produce an
alarm. |
| • Angle of View |
The scene angle that a video camera lens can show on the monitor, like
Diagonal Angle, Horizontal Angle and Vertical Angle, usually described in
degree. |
| • Anti-aliasing |
A procedure employed to eliminate or reduce (by smoothing and filtering)
the aliasing effects. |
| • Aperture |
The light gathering area of a lens, controlled by the iris. |
| • Auto-Focus Lens |
Automatically adjusts the lens focus from surrounding scene and keeps a
moving object in focus. |
• Automatic Gain
Control (AGC) |
This is a feature of many CCTV cameras that helps keep the strength of
the output signal constant, even when the light level changes. In other
words, it boosts the signal strength at low light levels, and caps it at
higher levels. |
| • Auto Iris (AI) |
Cameras with an Auto Iris feature, have the ability to compensate for
large variations in light levels. Particularly useful for cameras that need
to compensate for changes from bright sunlight to dark shadows. The auto
iris circuitry is normally linked to a motorised iris drive that physically
opens and shuts the iris on the lens. Closing a physical iris is a much
better way to protect a camera from being damaged by bright sunlight then
simply using electronics to reduce the signal strength. |
• Automatic White
Balance (AWB) |
This is a feature of some cameras that automatically adjusts the color
settings to maintain the quality of the white areas of the image. |
| • Back Focus |
This is the alignment of the rear of the lens to the imaging device. |
• Back Light
Compensation (BLC) |
This is a feature of cameras that automatically adjusts the image to
compensate for bright sunlight or bright lights, to give more detail on the
darker areas of the image. For example to focus on the detail of a face of a
person that has the sunlight shining from behind. |
| • Balun |
Balun stands for Balanced - Unbalanced. It is a device used to interface
between balanced lines and unbalanced lines. For example, twisted pair to
co-axial. |
| • BNC Connector |
BNC is a bayonet style connector for coaxial cable that is most commonly
used for CCTV installations. |
| • Brightness Control |
The manual bias control on a cathode ray tube or other display device
that controls the average brightness and the contrast of a picture. |
| • Camera Format |
Video camera's CCD chips format; 2/3", 1/3", 1/4", etc. |
| • Camera Sensor |
Video image sensor. CCD or C-MOS chip. |
| • CCD |
Charge Coupled Device. One of the two main types of image sensing device
used in cameras. It operates by converting light energy into electrical
charge. |
| • CCIR |
International Radio Consultative Committee; has made the technical
recommendation for the European 625 line standard for video signals. |
| • CCTV |
Closed Circuit Television. It does not broadcast TV signals but
transmits them over a closed circuit through electrically conducting cable
or wireless transmitter and receiver. |
| • CCTV Camera |
A unit containing an imaging device that produces a video signal in the
baseband form, usually with synchronization pulses and color information
(composite video). |
| • Chip |
An integrated circuit in which all the components (resistors capacitors
and semiconductors) are micro-fabricated on a tiny piece of silicon or
specialist material (silicon on sapphire. Often used to refer to the
detector in a CCD camera. |
• C Mount Lens & CS
Mount Lens |
CCTV lenses are available in two different lens mounts. "C-mount" lenses
have a flange back distance of 17.5mm vs. 12.5mm for "CS-mount" lenses. Many
of today's cameras can accept either type of lens, but it is important to
make sure that camera and lens. |
| • Coaxial Cable |
This refers to cable that has a central conductor, surrounded by a
shield sharing the same axis. The shield can be made from a variety of
materials including, braided copper, or lapped foil.
There are various standards for specific types of co-axial cable. The cable
used for normal CCTV installations is called RG59. |
| • Composite Video |
A combined signal in a television transmission. Standard format such as
NTSC, PAL or SECAM. The picture signal, blanking signal, and
vertical/horizontal synchronizing signals are all combined. |
| • Compression |
Digital video pictures can be compressed with a number of techniques.
These include, JPEG, M-JPEG, MPEG and Wavelet. |
| • CRT |
Cathode Ray Tube. The vacuum tube part of a monitor or television. |
| • Date/Time Generator |
Installed between a CCTV camera and a monitor, it generates the
information of Date, Time and camera ID. |
| • DC Power |
Direct Current Power; can be derived from an AC adapter or from a
battery. Among DC voltages of 6, 9, 12, 24, 28, 12VDC is most common in the
CCTV industry. |
| • Decibel (dB) |
The power or voltage ratio of two signals. |
• Digital Video
Recorder (DVR) |
Also known as a personal video recorder (PVR) or hard disk video
recorder. DVRs store recordings on a large hard drive, and most let you
pause and replay live television. When used with an electronic program guide
service, you can find and record shows automatically. |
| • Direct Drive (DD) |
Dynamic Host Configuration Protocol; lets network administrators manage
centrally and automate the assignment of IP addresses in an organization's
network. |
| • DHCP |
Dynamic Host Configuration Protocol; lets network administrators manage
centrally and automate the assignment of IP addresses in an organization's
network. |
| • DNS |
Domain Name System. A general purpose distributed, replicated, data
query service. Its principal use is the lookup of host IP addresses based on
host names. |
| • DSP |
Digital Signal Processing. It usually refers to the electronic circuit
section of a camera capable of processing or enhancing signals. |
| • Dwell Time |
The length of time a switcher displays one camera before sequencing to
the next. |
| • EIA |
Electronic Industries Association. American standard for B/W camera
system. |
| • Electronic Iris (EI) |
This is an electronic implementation of an auto iris. It uses
electronics to simulate the effect of opening and closing the iris, by
increasing or decreasing the effective shutter time of the camera. |
• Electronic Shutter
(ES) |
Compensates for moderate light changes in indoor applications without
the use of auto iris lenses. |
| • Ethernet |
The most widely installed Local Area Network (LAN) technology. Specified
in a standard IEEE802.3.10/100 BASE-T, the most commonly installed Ethernet
system, provides transmission speed up to 100 megabits per second. |
| • External Sync. |
An external sync allows a piece of equipment to take its video
synchronisation from another unit, so that it can align itself with the
system as a whole. |
| • Extranet |
A private network. It uses the Internet Protocol to securely share part
of a business information with suppliers, vendors or others. |
| • Field |
One video frame is composed of two fields; one field consists of the odd
numbered lines in the frame and the other field consists of the even
numbered lines. |
| • Focal Length (FL) |
The distance between the optical centre of a lens and the principal
convergent
focus point. |
| • Format |
The size of the cameras imager. Current standards are 1/2, 1/3, 1/4
inches. |
| • Frame |
A whole video image; is composed of two interlaced fields. A CCD chip
produces 30 frames per second at NTSC system and 25 frames at PAL. |
| • Gamma |
Degree of contrast in a video picture between output magnitude and input
magnitude. |
| • HAD |
Hole Accumulated Diode. A type of CCD sensor with a layer designed to
accumulate holes (in the electronic sense), thus reducing noise level. |
| • HDCP |
High-Bandwidth Digital Content Protection. HDCP encryption is used with
high-resolution signals over DVI and HDMI connections to prevent
unauthorized duplication of copyrighted material. |
| • HUB |
As a network product, a hub may include a group of modem cards for
dial-in users, a gateway card for connections to a Local Area Network (LAN),
and a connection to a line. |
| • ICMP |
Internet Control Message Protocol. A message control and error-reporting
protocol. |
| • Image Device |
The detector in the camera, either a tube or CCD solid state device. |
| • Image size |
Reference to the size of an image formed by the lens onto the camera
pickup device. The current standards are: 1", 2/3", 1/2" and 1/3" measured
diagonally. |
| • Interlace |
PAL video signals transmit odd and even lines alternately. This is a 2:1
interlace. The two sets of lines are combined to form each single frame. |
| • Internal Sync. |
Devices with internal sync, have an internal crystal to provide sync
pulses, without needing reference from any external device. |
| • Infra Red (IR) |
Low frequency light below the visible spectrum. This is often used for
covert or semi-covert surveillance to provide a light source for cameras to
record images in dark or zero light conditions. |
| • ISDN |
Integrated Service Digital Network. A set of standard for digital
transmission over ordinary telephone copper wire. |
| • IP |
Internet Protocol. A set of rules to send and receive messages at the
Internet address level. |
| • Iris |
This is a mechanical device that adjusts to vary the amount of light
passing through the lens of a camera. |
| • JPEG |
JPEG is a standard for coding/compression of still pictures. It is used
in the CCTV systems to compress and store individual frames of video. |
| • Lens |
An optical device for focusing a desired scene onto the imaging device
in a CCTV camera. |
| • Line Lock |
In CCTV, this usually refers to multiple cameras being powered by a
common
alternative current (AC) source (either 24 V AC, 110 V AC or 240 V AC) and
consequently have field frequencies locked to the same AC source frequency
(50 Hz in CCIR systems and 60 Hz in EIA systems). |
| • Loop |
This refers to connecting an additional device in parallel with an
existing video cable. For example, when driving a video recorder as well as
a monitor from the same video signal. |
| • Lux |
Light unit for measuring illumination. It is defined as the illumination
of a surface when luminous flux of 1 lumen falls on an area of 1 m2. It is
also known as lumens per square meter. One lux is equal to approximately
0.09290 foot candle. |
| • Matrix Switcher |
This is a device that allows any of its camera inputs to be switched to
one or more of its monitor outputs. The outputs can of course also be video
recorders. |
| • Monitor |
The device used to view video pictures. These devices do not normally
have television RF frequency receivers. They normally have composite, or
component video inputs. |
| • Monochrome |
This refers to a black and white image rather than a color one. |
| • Motorized Lens |
A camera lens equipped with small electric motor that enables focusing
lens, opening or closing the iris diaphragm, or changing the focal length.
|
| • MPEG |
MPEG is a standard used for coding and compression of moving images. It
was developed by the Moving Pictures Experts Group. It is now used widely
for the compression of video images. However MPEG isn't just one standard.
They have developed several standards for different uses. For example MPEG-2
is used for DVD's and set top boxes. MPEG-4 was developed for multi-media
applications for fixed and mobile web applications. |
| • Multiplexer |
This is a device that takes inputs from 2 or more video channels and
combines them into one signal. This is often done by using time division
multiplexing, which interleaves frames from each channel in such a way that
they can be split out again. Frequency division multiplexing uses different
frequencies to achieve the separation of the signals. |
| • Network Camera |
This refers to a camera that is designed to record pictures and transmit
them directly over a computer network or dialup internet connection. Network
cameras normally do not have any analogue video outputs. The images are
encoded directly in one of the standard compression techniques, such as JPEG
or MPEG. |
| • Noise |
Undesired signals that corrupt the original video signals and may reduce
the image quality. |
| • NTSC |
This is standard for TV signals developed by the National Television
Standards Committee in the USA. The UK and Europe, use a similar, but
different standard known as PAL. |
| • PAL |
This is the standard for TV signals used in the UK. It stands for Phase
Alternating Line. |
| • Pan and Tilt |
A camera mounting device that allows movement in both side ways and up
or down. |
| • Pinhole Lens |
This is a type of lens with a very small aperture. Normally used for
covert applications, where it can easily hide behind or within another
object. |
| • Pixel |
The smallest cell or area in a picture. The greater number of pixels,
the higher the resolution of the scene. |
| • PPPoE |
Point-to-Point Protocol over Ethernet. |
| • Protocol |
A specific set of rules, procedures or conventions relating to format
and timing of data transmission between two devices. A standard procedure
that two data devices must accept and use to be able to understand each
other. |
| • Quad |
A device that compresses up to 4 video signals and simultaneously
displays them on a monitor. |
| • RARP |
Reverse Address Resolution Protocol. For host machines that don't know
their IP address. |
| • RCA |
A device on the internet that determines the next network point to which
a data should be forwarded. |
| • Remote control |
A transmitting and receiving of signals for controlling remote devices
such as pan and tilt units, lens functions, wash and wipe control and
similar. It may also refer to the hand held controls for some VCRs and other
CCTV equipment. |
| • Router |
A device on the internet that determines the next network point to which
a data should be forwarded. |
| • RS-232 |
A format of digital communication using a three wire unbalanced
presentation.
The RS-232 standard defines the presentation and voltages for asynchronous
communications, but it does not define how the data should be represented by
the bits, i.e., it does not define the overall message format and protocol.
It is very often used in computers, CCTV and communications between
keyboards and matrix switchers. |
| • RS-422 |
This is an advanced format of digital communication when compared to
RS-232.
A major difference is that the presentation is balanced line and the
signaling is differential. In simple terms, the signal transmitted is read
at the receiving end as the difference between the two wires without a
reference to earth. So if there is common mode noise induced along the
line, it will be cancelled out. RS-422 can drive lines of up to 1200m and
distribute data on to up to 10 receivers. |
| • RS-485 |
This is an advanced format of digital communications compared to RS-232.
It is a balanced line transmission system. The major improvement over RS422
is in the number of receivers that can be driven with this format, up to 32. |
| • Serial Interface |
A digital communications interface in which data are transmitted and
received sequentially along a single wire or pair of wires. Common serial
interface standards are RS-232 and RS-422. |
| • S/N Ratio |
Signal to Noise Ratio. This is the ratio between the signal strength and
the noise levels on an audio or video signal. |
| • SMTP |
Simple Mail Transfer Protocol. TCP/IP used in sending and receiving
e-mail. |
| • S-Video |
Transmits luminance and color portions separately, using multiple wires,
thus avoiding the color encoding process and its inevitable loss of picture
quality. |
| • TCP/IP |
Transmission Control Protocol / Internet Protocol. The basic
communication language or protocol of the Internet. |
| • Time/Date Generator |
Installed between a CCTV camera and a monitor, it generates the
information of Date, Time and camera ID. |
| • Time-Lapse VCR |
Video recorder that can record frames with pauses between them thereby
extending the time that a standard cassette will hold. |
| • Termination |
This refers to a 75 Ohm terminator that is used to terminate each end of
a video line. |
• Television Lines
(TVL) |
This is a measure of the resolution of a video device. Higher number is
higher resolution. 380 TVL is considered medium resolution. 470 TVL or
greater is considered high resolution. |
| • Twisted-pair |
A cable composed of two small insulated conductors twisted together.
Since both wires have nearly equal exposure to any interference, common mode
noise is high, but the differential noise is slight thus common mode noise
is rejected in a twisted pair line. Twisted pair cable is used for balanced
line transmission. |
| • Vari-Focal |
This refers to a type of lens that has the facility to change the focal
length. This allows adjustment of the magnification and field of view of the
camera. |
• Videocassette
Recorder (VCR) |
A device that accepts signals from a video camera / microphone and
records video/audio on magnetic tape in a cassette. The VCR can play back
recorded video/audio on a television set or CCTV monitor. |
| • Motion Detection |
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 Switcher |
Switcher or Sequential Switcher. A device that allows the video signals
from multiple cameras to be displayed on a monitor, or recorded on a VCR one
at a time in sequence. |
| • Video Server |
This is a device that accepts inputs from CCTV cameras using the PAL,
composite video signal. It digitizes the signal and then transmits images
via a network, dialup or GSM connection. Advanced video servers have
built-in video motion detection, and can buffer images while they are being
uploaded to a remote server, where they are recorded. |
| • Wavelets |
This is a compression technique used to give high compression without
degrading the image quality. |
| • Y/C |
A method of sending video pictures in 2 separate parts down 2 separate
cables. The component parts are Y and C. |
| • Zoom Lens |
A lens of continuously variable focal length. |
| • Zoom ratio |
The ratio of the starting focal length (wide position) to the ending
focal length (telephoto position) of a zoom lens. A lens with a 10X zoom
ratio will magnify the image at the wide angle end by 10 times. |
