CCTV Glossary


In digital signal processing, anti-aliasing is the technique of minimizing aliasing (jagged or blocky patterns) when representing a high-resolution signal at a lower resolution


A system for detecting errors in color 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 with a mechanical iris which is controlled by a motor or other electrical device and responds to the changing video levels produced by a camera. The iris will be driven more open as the light hitting the image device becomes less and less and visa versa with an increase in light. The lens automatically adjusts the amount of light reaching the imager.


Any action initiated or controlled by an electronic circuit without manual intervention.


A process by which gain is automatically adjusted as a function of input or other specified parameter.


This is a device used to match or transform an unbalanced coaxial cable to a balanced twisted pair system. Lets one run a video signal over (cat 5) computer networking cable.


The defocusing of regions of the picture where the brightness is at an excessive level, due to enlargement of spot size and halation of the fluorescent screen of the cathode-ray picture tube. In a camera, sensor element saturation and excess which causes widening of the spatial representation of a spot light source.


A term used to describe a type of automatic sequential switcher which has the ability to send a signal to two monitors (dual output) one continually sequencing and the second one able to display any one of the camera inputs on the “bridged” monitor. There are two methods of bridging a second monitor. The first is passive where the video signal is “T”ed off the incoming line and sent to the second monitor, in this case the “bridged” monitor must be unterminated. The second method is active where the video signal is regenerated by a distribution amplifier in the switcher and sent to the “bridged” monitor in which case the monitor must be terminated. The bridging switchers are not always marked as being active or passive so attention must be given to the video signal on the “bridged” monitor to be sure if the termination must be set to on or off.


Also called burn. An image which persists in a fixed position in the output signal of a camera tube after the camera has been turned to a different scene or, on a monitor screen.


Refers to the image pick-up device size (1”, 2/3”, &Mac189;” and 1/3”). The format of the camera determines the type and size of lens used for the desired scene.


An environmental protective enclosure for a cctv camera. Can include a heater for winter and blower for summer.


Common abbreviation for Closed-Circuit Television.


In the CCTV industry, refers to a solid state camera (e.g. CCD).


That portion of the NTSC color television signal which contains the color information.


The degree to which a color is free of white or any other color. In reference to the operation of a tri-color picture tube it refers to the production of pure red, green or blue illumination of the phosphor dot face plate.


A video signal comprised of all elements which make up a standard NTSC video signal, including sync, horizontal and vertical timing pulses, black level and video level from reference black to peak white. If color is a factor then color burst will also be present in the composite video signal.


The ratio between the whitest and blackest portions of television image.


A specific “window” of distance in which objects remain in focus. Example – a camera’s field of view will present a picture encompassing a distance of 200 feet from the camera; objects in the picture are in focus at a distance of 10 feet to 90 feet within the picture. The window or depth of field is 80 feet for this example. The depth of field will change in relation to the change in F-stop where the depth of field increase as the F-stop increases (F-numbers get larger).


This is the latest form of recording and 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 event and does not require swapping of tapes.


The deviation of the received signal waveform from that of the original transmitted waveform.


The length of time a picture from a single camera stays on the screen. Usually associated with automatic sequential switchers.


Electronic Industry Association. US TV standard 525 lines 60 fields.


“Light Factor (f)”. The ability of a camera lens to pass light. A value used to indicate the speed of a lens where the smaller the number the better the lens “a fast lens”, the normal f stop in CCTV lenses is f/1.4 or f/1.2. Each increase in f-stop decreases the amount of light passed through the lens by 50%. The normal f-stops are: f/1.0 – f/1.4 – f.


The width and height or area desired to be covered by one camera. This area is determined by the focal length of the lens on the camera and the distance the camera is mounted from the scene.


A measure of light intensity. A unit of illuminance on a surface that is everywhere one foot from a uniform point source of light of one candle and equal to one lumen per square foot.


In video it is one still picture with a duration or dwell time of 1/30th of a second made up of 525 horizontal lines. A frame is made from two fields each having 262 &Mac189; horizontal lines which are interlaced. The video frame is similar to one still picture of a motion picture film.


An increase in voltage or power, usually expressed in dB.


To provide for a linear transfer characteristic from input to output device.


A pattern of vertical bars with shades of gray starting with white and gradually getting darker gray until ending at black. Most gray scales used in television have 10 steps or bars. The pattern is used to test the ability of a camera to reproduce true white, black and the varying steps of gray in-between.


A term used to describe a type of automatic sequential switcher which will stop sequencing and remain on a single camera input displayed on the monitor when a switch or button is depressed which is identified with the desired camera to be displayed. This switcher has only one monitor output.


Corresponds to colors such as red, blue, etcetera.


Impedance is a value of a circuit expressed in ohms, but is arrived at by the combination of resistance, capacitance and inductance. The symbol for impedance is “Z”. This term is used with reference to cable as well as electronics, example: RG59 coaxial cable has an impedance of 75 ohms. The input or output characteristic of a system component that determines the type of transmission cable to be used. The cable used must have the same characteristic impedance as the component. Expressed in ohms. Video distribution has standardized on 75-ohm coaxial and 124-ohm balanced cable.


Extraneous energy which tends to interfere with the reception of the desired signals.


A scanning process for reducing image flicker in which the distance from center to center of successively scanned lines is two or more times the nominal line width, and in which the adjacent lines belong to different fields.


The Internet Protocol address; a unique numeric address such as Also see Static IP and Dynamic IP.


An adjustable aperture built into a camera lens to permit control of the amount light passing through the lens.


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.


Refers to the ability of a lens to transmit light, represented as the ratio of the focal length to the diameter of the lens. A fast lens would be rated <f/1.4; a much slower lens might be designated as >f/8. The larger the f number, the slower the lens.


An amplifier for audio or video signals that feeds a transmission line; also called program amplifier.


Referring to the video inputs on a device such as a switcher or quad. The input is not terminated and has provisions to continue the video line, normally two BNC connectors are present on the rear of the device making it possible to connect the video signal to additional devices. The looping of a video signal should be limited to a few devices depending on distance between devices.


Distortion effects which occur at low frequencies. In television, generally considered as any frequency below the 15.75-kHz line frequency.


That portion of the NTSC color television signal which contains the luminance or brightness information.


A term used with regard to lenses and has evolved to be the same with “power” when describing the size of a zoom lens. A 16 to 160 mm lens is said to be a 10X or ten power zoom lens. It has a magnification of 10. The other standard is a 6X lens like a 12.5-75 mm. The largest mm is divided by the shortest mm to give the power or magnification.


Referring to a type of video switcher, which can be passive or active, with multiple cameras in and one monitor out, which requires buttons or switches to be pressed to change the camera displayed on the monitor.

Referring to types of lenses, meaning non-auto iris but manual adjust iris; also describing the zoom function of non-motorized zoom lenses.


A unit of equipment that displays on the face of a picture tube the images detected and transmitted by a television camera.


In monochrome television, a signal wave for controlling the brightness values in the picture. In color television, that part of the signal wave which has major control of the brightness values of the picture, whether displayed in color or in monochrome.


A unit that can accept a number of camera inputs and almost simultaneously display them on a single monitor and/or record them to a single video tape. Multixplexers can also be used to transmit multiple cameras over the same transmission medium.


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”.


The signal level at the output of an amplifier or other device.


A device upon which a camera can be mounted that allows movement in both the azimuth (pan) and in the vertical plane (tilt).


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 pre-selected scene automatically.


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