CCTV Glossary of Terms
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The world of Analogue CCTV, IP CCTV and HD CCTV can be highly complex, with various ideas and terms which can be confusing. However, we have compiled a brief glossary for reference. This list is not exhaustive but we’re working on making it as substantive as possible. If you would like further explanations about some of the terms or technology below, please get in touch.
Each CCTV device has its own power requirements (usually 12 volts and a current). The power coming out of the wall (in the UK) is 240 AC. The adaptor converts the AC power to DC power and will adjust it to a specified amperage.
Automatic Gain Control. A circuit for automatically controlling amplifier gain in order to maintain a constant output voltage with a varying input voltage within a predetermined range of input to output variation.
An input connection that triggers the unit to start recording if the alarm is triggered.
There are two main ways of doing things electronically, analogue or digital. An analogue signal can be represented as a series of sine waves. The term originated because the modulation of the carrier wave is analogous to the fluctuations of the human voice or other sound that is being transmitted.
Angle of view
For security cameras, this refers to the angular range in degrees that you can focus the camera on without distorting the image. When focusing close up, you can generally see a wide angle of view. If the focus is distant, the angle of view is smaller or narrower.
In television optics, it is the effective diameter of the lens that controls the amount of light reaching the photoconductive or photo emitting image pickup sensor.
Audio/Video Interleave (AVI)
An AVI file is a sound and motion picture file that conforms to the Microsoft Windows Resource Interchange File Format (RIFF) specification. AVI files require a special player that may be included with your web browser.
A system for detecting errors in colour balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction.
A lens in which the aperture automatically opens or closes to maintain proper light levels on the faceplate of the camera pickup device.
Automatic Brightness Control
In display devices, the self-acting mechanism which controls brightness of the device as a function of ambient light.
Automatic Gain Control
A process by which gain is automatically adjusted as a function of input or other specified parameter.
Automatic Iris Lens
A lens that automatically adjusts the amount of light reaching the imager.
Automatic Light Control
The process by which the illumination incident upon the face of a pickup device is automatically adjusted as a function of scene brightness.
Automatic White Balance
A feature on colour cameras that constantly monitors the light and adjusts its colour to maintain white areas.
Back Light Compensation (BLC)
A feature on newer CCD cameras which electronically compensates for high background lighting to give detail.
The bandwidth determines the rate at which video can be sent through a network the greater the bandwidth, the more video that can be sent in a given amount of time. Usually measured in bits-per-second.
The baud rate is how many bits can be sent or received per second.
Is a type of connector used to interconnect two coaxial cables or connect a cable with other CCTV components
The attribute of visual perception in accordance with which an area appear to emit more of less light. (Luminance is the recommended name for the photoelectric quantity which has also been called brightness.)
Category (CAT) 5 Cable
Cable that is capable of transmitting data at high speeds (100 megabits per second and faster). CAT 5 cable is commonly used for voice and data applications. Usually comes with RJ45 connectors.
Common abbreviation for Closed Circuit Television.
Charge Coupled Device
CCTV cameras that are CCD will give sharper, better-defined pictures.
Complementary Metal Oxide Semiconductor. Similar to a CCD, it also detects light for conversion into a signal. Lesser image clarity than CCD, but more compact in size with lower power usage.
A particular type of cable capable of passing a wide range of frequencies with very low signal loss. Such a cable in its simplest form, consists of a hollow metallic shield with a single wire accurately placed along the centre of the shield and isolated from the shield.
Short for compressor/decompressor, a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both. Examples of Codecs include Wavelet, MPEG4, JPEG.
Composite Video Signal
The combined picture signal, including vertical and horizontal blanking and synchronizing signals.
This is the Codecs used for compressing and decompressing video data.
The range of light to dark values in a picture or the ratio between the maximum and minimum brightness values.
`Day/Night Cameras` are regular cameras with an especially sensitive CCD chip that allows a good image to be captured in very low ambient lighting (regular lighting not infrared).
The fidelity of a television system to the original scene.
Depth of Field
The in-focus range of a lens or optical system. It is measured from the distance behind an object to the distance in front of the object when the viewing lens shows the object to be in focus.
Digital Video Recorder (DVR)
A digital video recorder is basically a computer that converts the incoming (analogue) signal from the cameras to digital, and compresses it, and stores it. The DVR replaces the function of a multiplexer (or quad or switcher) and a security VCR. There are many advantages of digital video recorders over their analogue counterparts.
The deviation of the received signal waveform from that of the original transmitted waveform.
A device that provides several isolated outputs from one looping or bridging input, and has a sufficiently high input impedance and input to output isolation to prevent loading of the input source.
A circuit that permits transmission in both directions. In CCTV, duplex is often used to describe the type of multiplexer that can perform two functions simultaneously: recording in multiplex mode and playback in multiplex mode
Dynamic IP address
The term used to describe how an IP address is dynamically assigned to computers as and when needed. Unlike Static IP addresses, the IP address is temporary e.g. when you connect to your ISP using a dialup connection , you PC or router will be dynamically assigned an IP address whilst you are online.
One of the two equal but vertically separated parts into which a television frame is divided in an interlaced system of scanning. A period of 1/60 second separates each field start time.
Field of View
The maximum angle of view that can be seen through a lens or optical instrument.
Of a lens, the distance from the focal point to the principal point of the lens.
A plane (through the focal point) at right angles to the principal point of the lens.
The point at which a lens or mirror will focus parallel incident radiation.
The total area, occupied by the television picture, which is scanned while the picture signal is not blanked.
Frames per Second (fps)
This refers to the number of pictures that can be recorded or displayed per second. A television displays 25fps and is referred to as real time. This should not be confused with fields per second. Two fields per second are equivalent to one frame per second. Recommended frame rates are as follows:
POS Monitoring = 25fps
Retail Surveillance = 16fps
Door/Car Monitoring = 4fps
An increase in voltage or power, usually expressed in dB.
A piece of hardware that acts between a LAN and the internet. The Gateway address is simply the IP address of the Gateway.
Ghost or “ghosting”
A spurious image resulting from an echo.
This unit is typically used to measure large data storage or data transfer capacities (by current standards). 1GB = 1024 MB = 1,048,576 KB = 1,073,741,824 bytes.
It is generated from MPEG4, but more advanced for video compression. It has more complex coding algorithm, lower usage of bandwidth and smaller royal fee than MPEG4. It works well on a very wide variety of applications, networks and systems (e.g., for broadcast, DVD storage, and multimedia telephony systems).
Hard Disk Drive (HDD)
The storage device usually fixed inside of your computer or DVR used to store information.
IP (Internet Protocol)
The TCP/IP standard protocol that defines the IP datagram as the unit of information passed across an Internet and provides the basis for connectionless packet delivery service.
The numeric address of a computer on the Internet. An IP address is written as a set of four numbers separated by periods (each number can range from 0 to 255). An example of an IP address is 126.96.36.199
Infra Red Camera
Infrared cameras (night vision cameras) have special infrared lights installed around the perimeter of the camera lens. This provides special light that the camera uses to capture a good picture even in total darkness.
Extraneous energy which tends to interfere with the reception of the desired signals.
An adjustable aperture built into a camera lens to permit control of the amount of light passing through the lens.
stands for `Joint Photographic Experts Group` who designed the standard. This is a standard way of compressing images which works particularly well for photographic images (as opposed to graphic art).
JPEG2000 is image coding system and the successor of the JPEG format. Its architecture lends itself to a wide range of uses from portable digital cameras to advanced prepress, medical imaging and other key sectors. Compared to JPEG, JPEG2000 offers higher compression without compromising quality, progressive image reconstruction.
LAN (Local Area Network)
A communications system that links computers into a network, usually via a wiring based cabling scheme. LANs connect PCs, workstations and servers together to allow users to communicate and share resources like hard disk storage and printers. Devices linked by a LAN may be on the same floor or within a building or campus. It is user owned and does not run over leased lines, though a LAN may have gateways to the PSTN or other, private, networks.
LED Light Emitting Device
is a type of light source which generates an infrared frequency when stimulated by electricity.
Liquid Crystal Display. Liquid crystal displays (LCDs) offer several advantages over traditional cathode-ray tube displays that make them ideal for several applications. LCD’s are flat, and they use only a fraction of the power required by CRTs. They are easier to read and more pleasant to work with for long periods of time than most ordinary video monitors. There are several trade-offs as well, such as limited view angle, brightness, and contrast, not to mention high manufacturing cost.
A transparent optical component consisting of one or more pieces of optical glass with surfaces so curved (usually Spherical), that they serve to converge or diverge the transmitted rays of an object, thus forming a real or virtual image of that object.
Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm.
Also called looping. The method of feeding a series of high impedance circuits (such as multiple monitor/displays in parallel) from a pulse or video source with a coax transmission line in such a manner that the line is bridged (with minimum length stubs) and that the last unit properly terminates the line in its characteristic impedance. This minimizes discontinuities or reflections on the transmission line.
A reduction in signal level or strength, usually expressed in dB. Power dissipation serving no useful purpose.
Luminous intensity (photometric brightness) of any surface in a given direction per unit of projected area of the surface as viewed from that direction, measured in foot lamberts (fl).
International System (Sl) unit of illumination in which the meter is the unit of length. One lux equals one lumen per square meter. A camera`s light gathering ability. The lower the number, the better the image in low light conditions. A sunny day would be about 100,000 lux a full moon at night would be about 0.1 lux street lighting would be about 1 to 10 lux home/office lighting would be about 100 to 1000 lux.
Megabits Per Second (MBPS)
A measurement of the transmission speed of data measured in 1,048,576 bits per second.
Motion Joint Photographic Experts Group (MJPEG)
This compression standard generally refers to JPEG images shown at high frame rate, generally 25 frames per second. It gives high quality video images, but the comparatively large file sizes of each individual image does put demands on the transmission bandwidth.
device for the transmission of data via dialup networking.
The process, or results of the process, whereby some characteristic of one signal is varied in accordance with another signal. The modulated signal is called the carrier. The carrier may be modulated in three fundamental ways: by varying the amplitude, called amplitude modulation; by varying the frequency, called frequency modulation; by varying the phase, called phase modulation.
A unit of equipment that displays on the face of a picture tube the images detected and transmitted by a television camera.
Black and white with all shades of grey.
Motion Picture Experts Group (MPEG)
MPEG is an international standard for video compression. MPEG1 is a low-resolution format currently used on the World Wide Web for short animated files. MPEG2 is a much higher resolution format being developed for digital television and movies. MPEG4 is increasingly being used in CCTV solutions.
MPEG4 is a graphics and video compression algorithm. It is further development of the MPEG2. MPEG4 resolves the picture more effectively and can thus compress sequence quicker and maybe smaller. Now, it is popularly used for Internet transmitting.
A device primarily developed as a means to record multiple cameras simultaneously to a single videotape. They also allow viewing of multiple cameras on a single monitor in various arrangements.
Cameras that have night vision have the ability to see in low light conditions. To judge how dark it can be for your camera to work, look at the Lux rating on the camera. The lower the lux, the better it will see at night.
The word `noise` originated in audio practice and refers to random spurts of electrical energy or interference. In some cases, it will produce a `salt-and-pepper` pattern over the televised picture. Heavy noise is sometimes referred to as `snow`.
A video signal containing all information except sync.
Abbreviation for National Television Systems Committee. A committee that worked with the FCC in formulating standards for the present day United States colour television system.
The signal level at the output of an amplifier or other device
The UK’s colour television standard. Abbreviation of “Phase Alternative Line”
Pan and Tilt
A device upon which a camera can be mounted that allows movement in both the azimuth (pan) and in the vertical plane (tilt).
Pan/Tilt Preset Positioning
Follower pots are installed on pan/tilt unit to allow feedback to the controller and provides information relevant to horizontal and vertical positioning, allowing the controller to quickly adjust to a preselected scene automatically.
PCI Video Card
A PC card that allows video from analogue cameras to be fed into a computer.
Passive Infrared. Widely used in devices to detect motion. A special lens on the front of the PIR divides the sensor into zones. A individuals body heat radiation is detected as it moves through the sensor zones in front of the PIR
Short for Picture Element. A pixel is the smallest area of a television picture capable of being delineated by an electrical signal passed through the system of part thereof. The number of picture elements (pixels) in a complete picture, and their geometric characteristics of vertical height and horizontal width, provide information on the total amount of detail which the raster can display and on the sharpness of the detail, respectively. Monitor resolution is measured in pixels. CCTV pictures of 640 x 480 pixels (full screen) and 320 x 240 (quad screen) are most common.
This refers to pointing a port of a modem/router to an IP address where a PC or networked DVR can be found for viewing cameras over the internet.
When data is being transmitted between two or more devices something needs to govern the controls that keep this data intact. A protocol is a formal description of message formats and the rules two computers must follow to exchange those messages.
is a device which uses digital video to display pictures from 4 cameras on a single monitor.
A type of telephone connector. Standard in the US.
A standard network connector, often found at the end of CAT5 cable.
Real time video
is a picture with 25 frames per sec and therefore looks continuous
The amount of resolvable detail in the horizontal direction in a picture. It is usually expressed as the number of distinct vertical lines, alternately black and white, which can be seen in a distance equal to picture height.
The details that can be distinguished on the television screen. Vertical resolution refers to the number of horizontal black and white lines that can be resolved in the picture height. Horizontal resolution refers to the black and white lines resolved in a dimension equal to the vertical height and may be limited by the video amplifier bandwidth.
The amount of resolvable detail in the vertical direction in a picture. It is usually expressed as the number of distinct horizontal lines, alternately black and white, which can theoretically be seen in a picture.
Also called image burn. A change produced in or on the target which remains for a large number of frames after the removal of a previously stationary light image and which yields a spurious electrical signal corresponding to that light image.
is a measure of picture definition and clarity and is represented by number of lines. Greater the number of lines, higher the resolution.
is a type of coaxial cable used for transmission of video signals up to 230m. It is the most popular cable used in CCTV.
RF (Radio Frequency)
A frequency at which coherent electromagnetic radiation of energy is useful for communication purposes. Also, the entire range of such frequencies.
A loss of vertical synchronization which causes the picture to move up or down on a receiver or monitor.
The role of a router can be described as a bridge between two or more networks. The function of the router is to look at the destination addresses of the packets passing through it, and thereafter decide which route to send these packets on.
A standard for serial transmission of data between two devices. This defines the pin and plug in terms of size, shape and number of pins.
In colour, the degree to which a colour is diluted with white light or is pure. The vividness of a colour, described by such terms as bright, deep, pastel, pale, etc. Saturation is directly related to the amplitude of the chrominance signal.
The process of moving the electron beam of a pickup tube or a picture tube across the target or screen area of a tube. Sensitivity In television, a factor expressing the incident illumination upon a specified scene required to produce a specified picture signal at the output terminals of a television camera.
Standard European 20 pin connector used for carrying both video and audio signals in domestic TV appliances, now utilised on some CCTV equipment
Also known as a communications port or COM port. The serial port is a location for sending and receiving serial data transmissions. These ports are known by the names COM1, COM2, COM3, and COM4.
Ability to control the integration (of light) time to the sensor to less than 1/60 second; e.g. stop motion of moving traffic.
Signal to Noise Ratio
The ratio between useful television signal and disturbing noise or snow.
Heavy random noise.
A transient of short duration, comprising part of a pulse, during which the amplitude considerably exceeds the average amplitude of the pulse.
Static IP address
An IP address which is the same every time you log on to the Internet. The alternative to a dynamic IP address. Often standard for business broadband but not for domestic broadband.
A numeric designation, with the same format as an IP address, which determines how much of an IP address is used to partition a network using TCP/IP into smaller entities called subnets.
A chart especially prepared for checking overall performance of a television system. It contains various combinations of lines and geometric shapes. The camera is focused on the chart, and the pattern is viewed at the monitor for fidelity.
is a device which generates time and a date superimposes it on the video signal.
Time Lapse VCR
A video recorder, most often in the VHS format, that can slow down the recording process and create a time lapse between recorded frames. This increases the amount of recording time on an individual tape. Unlike a standard VCR which has a maximum recoding time of 8 hours, time-lapse recorders can record from 2 to 960 hours on a standard VHS tape. Recording speeds available on some Time Lapse VCR
Transmission Control Protocol/ Internet Protocol (TCP/IP)
The protocols, or conventions, that computers use to communicate over the Internet.
TV Line Resolution
the number of distinct horizontal lines, alternately black and white, which can theoretically be seen in a picture. Allows a buyer to judge the quality of any camera. Low resolution is between 300 and 380, medium resolution is between 400 and 480, high resolution is 480 plus
Universal Serial Bus (USB)
A standard port that enables you to easily connect external devices (such as digital cameras, scanners, and mice) to a PC.
The uploading of data from your PC to the Internet. ADSL has both upstream and downstream data rates.
is a type of manual zoom lens with a small zoom ratio (ranging between 4mm to 12mm depending on brand). It is used when the focal length of the lens needs to be fine tuned to meet the requirements of the actual scene
A unit, when used with a PIR camera, will automatically instruct your domestic video to record. After motion has stopped, the VCR Activator will stop your video recording.
Vertical Resolution (TVL)
The number of horizontal lines that can be seen in the reproduced image of a television pattern.
A wideband amplifier used for passing picture signals.
The frequency bandwidth utilized to transmit a composite video signal.
Video Capture Card
Computer cards that you can install on the motherboard of your own computer to create your own video recording computer.
Video Graphics Array (VGA)
The display standard for PC monitors. VGA outputs are compatible with PC monitors.
Video Motion Detection (VMD)
A method for detecting motion in a video image by checking to see if the pixels in the video image have changed.
Video Signal (NonComposite)
The picture signal. A signal containing visual information and horizontal and vertical blanking (see also Composite Video Signal) but not sync.
A video server compresses video signal from analogue cameras to allow them to be viewed over a network such as a LAN or the internet.
A mathematical codec useful in image compression. In the Internet, wavelet has been used to compress images to a greater extent than is generally possible with other methods such as JPEG or MPEG.
A DVR or Software system with a built-in web server allows you to view cameras over an internet browser.
Wireless cameras allow the transmission of video and audio data to be transmitted to the receiver without having to run wires (using radio waves). Wireless cameras often have an option to power the camera via mains in which case there will be a lead from camera to power point
A camera that transmits its signal via cable back to the recording/control device. Some wired cameras use composite cable (taking both the video and power signal) whilst some have separate power and video cables.
A signal transmitted in colour television containing brightness information. This signal produces a black and white picture on a standard monochrome receiver. In a colour picture it supplies fine detail and brightness information.
To enlarge or reduce, on a continuously variable basis, the size of a televised image primarily by varying lens focal length.
An optical system of continuously variable focal length, the focal plane remaining in a fixed position.