Glossary of CCTV Surveillance Terms:
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.
Megabyte (MB)
1,048,576 bytes or 1,024 kilobytes. Used to measure computer memory. Sometimes used to mean 1 million bytes or 1,024,000 bytes (1,000 kilobytes). Also see Gigabyte.
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.
MPEG
MPEG is a video compression method commonly used in digital recording. MPEG-1 is a standard for CD-ROM video and audio. MPEG-2 is a standard for full-screen, broadcast quality video.MPEG-4 is a standard for video telephony.
Multiplex (Time Multiplex)
Using one carrier to send more than one signal. In video multiplexers, achieving this by sending a
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.
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.
RAID
Redundant Arrays of Independent Disks. The use of two or more disk drives instead of one disk, which provides better disk performance, error recovery, and fault tolerance, and includes interleaved storage techniques and mirroring of important data.
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 neede
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
SCSI
Small Computer Systems Interface (Pronounced "scuzzy".) A ultra high-speed interface that can connect to computer devices such as a hard drive or CD-Rom. A SCSI channel can connect up to seven devices.
Sensitivity
A cameras 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.
Solving Focus Shift
Filtering techniques can be applied to solve the problem of focus shift under active infrared lighting. Cameras behave differently under visible light and infrared light, with one of the chief differences being focal properties. Day-night mechanical filters solve this problem by blocking IR light from during the day and optimizing IR response during the night. The result is a sharply focused image in day and dark conditions.
Spot Filter
A small insert used in a lens to increase the f-stop range of the lens.
Static IP Address
A Static or Dedicated IP address is a type of account from an ISP where your computer or network is assigned the same constant IP Address at all times. Also see IP Address and Dynamic IP.
Switcher
A device used to switch the video signals from two or more cameras on a monitor.
Super HAD CCD
Super HAD (Hole Accumulation Diode) CCDs allow more light to pass to each pixel, increasing sensitivity and reducing noise.
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.
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.
Visible Light
Wavelengths of light visible to the human eye.
W
Wavelet
A digital file commonly used in digital recording, which contains a representation of sound waves in digital form; limited in duration and frequency.
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
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