CCTV Terms and Definitions

10 Jun

ALC (Automatic Level Control) On AL lenses, aka peak/average control. Adjusting this control allows the auto iris circuitry to either take bright spots

Activity Detection A feature of the generation 3 multiplexor range that uses video motion detection techniques to improve camera update

Alarming The ability of CCTV equipment to respond to an input signal, normally a simple switch closure. The response varies

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)

Aspherical Lens A lens designed with a non spherical shape so that it refracts the light passing through it 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 frequencies of an oscillator is automatically maintained within specific units,

Automatic Gain Control (AGC) An electronic circuit used whereby 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 cameras imager.

Auto-Terminating Feature whereby equipment automatically selects the correct termination depending on whether the video output is connected to

Back Lighting Compensation (BLC) A feature of modern CCD camera 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 a zoom lens to ensure the image stays in focus throughout the zoom range.

Balanced Signal Method of transmitting video, usual over twisted pair cable, that consists of two equal but opposite signals being sent down two semiconductors.

Bandwidth 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 fly back blanking) The operation of turning of the monitor display, or pick-up device, during sync pulses to avoid thin white lines that appear in 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 video connector in the CCTV industry

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 17.5 mm flange back distance. The CS-Mount lens has a 12.5 mm flange back distance.

CCIR 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 monitor that can reproduce the picture image seen by the camera.

CATV (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 semi-conductor 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 of carrying a wide range of frequencies (video and radio) with very low signal loss.

Composite Video The complete video signal consisting of the video information, the sync pulse and the threshold reference.

Contrast The range of light and dark values in a picture or the ratio between the maximum and minimum brightness values.

Cross talk An undesired signal that interferes with the desired signal

Decibel (Db) 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 lens.

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 Recording images on digital mediums such as optical or hard drives instead of analog tapes.

Distribution Amplifier A device that accepts a video signal and sends it out over a number of independent outputs.

Duplex Multiplexor A multiplexor with two frame stores allowing it to show multi-screen pictures while performing time multiplex recordings.

Dwell Time The length of time a switcher displays a camera before moving on to the next one in the sequence.

EI (Electronic Iris) Shutter The ability of the camera to compensate for moderate light changes in indoor applications without the use of an auto iris lens.

EIA (Electronic Industry Association) US TV standard 525 lines 60 fields.

Equalization The process of correcting losses of certain components in a signal.

External Sync The ability of CCTV equipment to accept one or more of the standard sync formats so as to align itself to the rest of the system

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 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 to the focal plane.

Focal Length The distance (in millimeters) from the lens to the surface of the imager. The shorted the distance, the wider the view, the longer the distance, the narrower the view.

Focus The focal point. An adjustment  to the lens optics to improve the images clarity.

Foot Candle (FC) A measurement of light. 1 lumen per square foot.

Format The size of the cameras imager. Current standards are 1/2, 1/3, 1/4 inches.

Frame A complete picture. 2 fields of video information.

F-Stop The speed of a lens. The smaller the f-number, the greater amount of light passing through the lens.

Gen. Lock (See External 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.

Grey Scale The number of variations from white to grey to black.

Ground An electrical connection point that is common to either a metal chassis, a terminal, or a ground bus.

Ground Loop Affects video pictures in the form of a black shadow bar across the screen or as tearing in the top corner of the picture. Caused by different earth potentials in the system.

Hardwired Method of controlling camera points using multi-core cables.

Horizontal Resolution The maximum number of individual picture elements that can be distinguished in a single scanning line.

Hertz (Hz) Cycles per second

IR (Infrared) A range of frequencies lower than visible red light used for covert surveillance or as a low cost wireless video link.

ISDN (Integrated Services Digital Network) Digital phone lines from which allow transmissions of video signals via fast scan at speeds of 128Kb / sec; used with terminal adapters.

Image Burn (Retained Image) A change produced or in or on a target pickup device (monitor) which remains after the removal of a previously stationary light source.

Image Device (Imager) The detector in the camera, either a tube or CCD solid state device.

Impedance The effective resistance of an electronic circuit to an AC 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.

Interlace A scanning process where every other horizontal line is scanned in one field while the alternate lines are scanned into 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 sources. Normally using a crystal controlled oscillator.

Iris The adjustable opening through which light can pass and is regulated.

Lens A transparent optical component that converges light rays to forma 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 this 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 a signal strength and quality due to long cable runs.

Line Lock Used 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 the video signal that consists of the monochromatic data.

Lux A unit of measurement for the intensity of light. One foot-candle (FC) = 10 Lux.

Manual Iris Lens A lens with a manual adjustment for the iris opening in a fixed position. Generally used for fixed lighting applications.

MATV Multiple Access Television. The method of distributing RF TV signals by broadcasting them through the air.

Mechanical focus (Back Focus, Racking) lenses that ensure the image stays in focus throughout the zoom range.

Microwave Radio frequencies between 1 and 30 Ghz.

Minimum Object Distance (MOD) The closest distance a given lens will able to focus upon.

Modulate to change or vary some parameter such as varying the amplitude of a signal. A modulator is the circuit that modulates the signal.

Monitor A device that converts electronic signals into the video image that was generate by a camera and lens. The picture end of a CCTV system.

Multiplex (Time Multiplex) Using one carrier to send more than one signal. In video Multiplexors this achieved by sending a different camera output in each successive field or frame of a video signal.

Mux A Multiplexor.

NTSC (National Television Standards Committee, see EIA) Color TV system used in the United States.

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.

PAL (Phase Alternate Line, see CCIR) Color TV system used in the United Kingdom.

PTSN (Public switched Telephone Network) Standard phone lines used to transmit fast scan pictures via modems.

Pan Side-to-side movement of a camera (horizontal axis).

Passive A non-powered element of a system.

Peak to Peak The amplitude difference between the most positive and the most negative incursions of a signal.

Peripheral An optional device that can enhance a CCTV system. (i.e. quad, VCR, multiplexor, etc…)

Phase Adjustment (See Line Lock) The ability to delay the line locking process so as to align cameras fed from AC voltages on a different phase.

Photocell Automatically switches on the infrared (IR) if ambient light levels fall below a preset level.

Pinhole Lens lens used for applications where the camera must be hidden. A 1/32 or 1/16 inch lens mounted on a camera that is capable of viewing an entire room.

PIP Picture in Picture

Pixel The smallest cell or area in a picture. The greater number of pixels, the higher the resolution of the scene.

Presets The pre-positioning of a pan, tilt, zoom camera by the use of its potentiometer.

Quad A device that compresses up to 4 video signals and simultaneously displays them on a monitor.

Rack Mount An industrial standard housing 19″ wide, its height is measure in units of U (1.75 inches ea)

RF (Radio Frequency) Signals with a repetition rate above audible hearing, but lowed than frequencies associated with heat and light.

Random Interlace A scanning technique in which there is no external control over the scanning process. 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 a monitor.

Raster The rectangular patter of scanning lines upon which the picture is produced. The illuminated face of the TV monitor without the 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 a television system to reproduce details.

Roll A loss of vertical sync which causes the picture to move up and down on a TV screen.

RS232 A commonly used computer serial interface.

SECAM (see CCIR) Color TV system used in France.

SVHS (Super Video Home System) New format high resolution VHS recorders. VHS compatible.

S/N (Signal to Noise Ratio) Measure of the noise levels of a video signal. The higher the number, the better.

Saturation (Color) The measure of the vividness of color. The amplitude of chrominance.

Scanner A panning only unit.

Scanning The rapid movement of an electronic beam in a pickup device of a camera or in the CRT of a television receiver. When referring to a video surveillance field, it is the horizontal panning camera motion.

Sensitivity A camera’s ability to reproduce a given scene with a given light level. Usually expressed in Lux or foot-candles.

Sequential Switchers A video device that alternates the displayed video image from one camera to the next. A video device that sequentially steps through and displays all connected camera signals.

Simplex (Multiplexor) A Mux with 1 frame store that can either multiplex record or show multi-screen pictures in live or play back mode. It cannot record multiplexed images while showing a multiplexed mode.

Spot Filter A small insert used in a lens to increase the F-Stop range of the lens.

Switcher See sequential Switchers above.

Sync Abbreviation for synchronization. Electronic pulses that are inserted into video signal for the purpose of assembling the picture in the correct position.

TVL (Television Lines Resolution) The maximum number of changes between light and dark pictures across 3/4 the width. Dictates the resolution of a CCTV product.

Tearing A picture condition in which the horizontal lines are displaced in a 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 (vertical) movement of a camera.

Time Zone Time intervals during which activity is permitted. Used digital motion setup.

TBC (Time Base Corrector) Electronic circuit that aligns the unsynced video signal before signal processing. Used in Muxs and quads.

Time-Lapse VCR Video recorder that can record frames with pauses between them thereby extending the time that a standard cassette will hold.

Triplex (Triplex Multiplexor) Mux feature that gives you the ability to simultaneously view both playback and live cameras within the same multiscreen while still recording.

Twisted Pair A cable, often screened, that consist of two conductors twisted together along their length.

UPS (Uninterruptible Power Supply) Equipment that supplies power to a system in the event of a primary power loss. It may consist of batteries or an auxiliary generator.

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 external coaxial cables.

Varifocal Lens See Zoom lens. Usually not motorized (manual)

VCR a device that records video information to a tape.

Vertical Interval Switching Sequential switchers waiting until the current field has finished before displaying the next camera even though the dwell time has elapsed.

Vext A Mux feature that uses a pulse generated by the VCR so that the MUX automatically adjusts to the VCR time lapse speed.

Video Motion Detection (VMD) 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 of images from a video signal.

Visible Light Wavelengths of light visible to the human eye.

White Light The entire spectrum of visible light.

Y/C A method of sending video pictures in 2 separate parts down 2 separate cables. The component parts are Y and C

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. Usually represented as a multiplier (i.e. 32x)

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