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Aberration: Any inherent deficiency of a lens or optical system. Aberrations are responsible for imperfections in shape or sharpness of the image.

Activity Detection: A feature of the Generation 3 video multiplexer range that uses video motion detection techniques to improve the camera update times. It also gives a relay closure.

AGC: Automatic Gain Control, an electronic circuit that amplifies the video signal when the strength of the signal falls below a given value.

Alarming: The ability of CCTV equipment to respond to an input signal, normally a simple switch closure. The response varies depending on equipment type, most common is for switcher to ‘hold’ on the camera corresponding to the alarm input.

ALC: Photometric control measures light intensity and determines the iris reaction sensitivity. Sensitivity is increased when the potentiometer is turned towards PEAK, and decreased when turned towards AVERAGE.

Analog: A signal in which any level is represented by a directly proportional voltage; not digital.

Angle of View: May be expressed in Diagonal, Horizontal, or Vertical. Smaller focal lengths give a wider angle of view.

Aperture: The opening of the lens that controls the amount of light reaching the surface of the pickup device. The size of the aperture is controlled by the iris adjustment.

Aperture Scale: The aperture scale is referred to as an F-number. The international aperture scale is: F1, F1.4, F2, F2.8, F4, F4.6, F8, F11, F16, etc.

Aspect Ratio: The ratio of the picture frame width to the picture frame height in standard TV systems. It is 4 units horizontal over 3 units vertical.

Aspherical Lens: A lens one or more of whose elements has a non-spherical surface. Aspherical surfaces are shaped to reduce the spherical and other aberrations.

Attenuation: A decrease or loss in a signal. Reduction of signal magnitude (loss) normally measured in decibels

Auto Iris Lens: A lens with an electronically controlled iris. This allows the lens to maintain one light level throughout varying light conditions.

Automatic Frequency Control (AFC): An electronic circuit used whereby the frequency of an oscillator is automatically maintained within specified limits.

Automatic Gain Control (AGC): An electronic circuit used by which the gain of a signal is automatically adjusted as a function of its input or other specified parameter.

Auto Terminating: Feature whereby the equipment automatically selects the correct termination depending on whether the video output BNC is connected.

Auto White Balance: Feature on color cameras whereby the camera constantly monitors the light and adjusts its color to maintain white areas.

Back Focus: A term used to describe the relationship of the distance of the lens to the image device. This distance is critical to maintaining the proper depth of field through changing focal lengths and varying light conditions. The correct back focus is normally achieved by adjusting the image pick-up device on the camera itself.

Base-Band Video: An 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 Blanking): Turning the monitor off during the sync pulse to avoid the thin white lines appearing on the picture.

BLC: Back light compensation. A function of the camera that compensates for excessive light directed at the camera, which causes the video to bloom or the images in front of the light to be unusable.

Blooming: The halo and de-focusing that occurs around the bright areas of the picture (highlight) whenever there is an increase in the brightness intensity is blooming.

BNC: One of the most popular of the coaxial connectors, the name BNC stands for Bayonet Neill Concelman. Bayonet describes the coupling mechanism, while Neill and Concelman were the inventors of the N and C connectors. BNC connectors are available in both 50 and 75 ohm versions, both versions will mate together. The 50 ohm designs operate up to a frequency of 4GHz. BNC connectors are used in many applications, some of which are flexible networks, instrumentation and computer/ peripheral interconnections. The 75 ohm version is used for CCTV and CATV applications.

C / CS mount: C - An industry standard for mounting a lens to a camera where a 1” x 32 thread is employed and the distance from the image plane is 17.52mm from the shoulder of the lens. A C-mount lens may be used CS-mount camera with the use of a 5mm-adapter ring. CS- A relatively new industry standard for mounting a lens to a camera where a 1" X 32 thread is employed and the distance from the image plane from the shoulder of the lens is 12.52mm. A CS-mount lens may not be used on a C-mount camera.

Camera Format: The size of a camera image pickup device. This measurement is derived from the diagonal line of a chip or the diameter of the tube. Currently there are five format sizes in the CCTV industry: 1", 2/3", 1/2", 1/3" and, 1/4".

Cathode Ray Tube (CRT): The picture tube in a video monitor that can reproduce the picture image seen by the camera.

CATV: Short for Cable Access Television. The method for distributing RF signals via coaxial cable rather than radiated through the air.

CCD - CCD (charge-coupled device) is a type of image sensor. In effect, it is the "eye" of a camera phone, digital camera, or video camera. It is a device similar to a computer chip, which senses light focused on its surface, like electronic film.

CCTV - CCTV is frequently used in video surveillance systems. CCTV (closed circuit television) is a television system in which signals are not publicly circulated; cameras are linked to television monitors in a restricted region such as a store, an office building, or on a college campus.

CCTV Surveillance System - Closed circuit television video surveillance systems are often used for security purposes.

Chrominance (C): The part of the video signal corresponding to the color information.

CIF (Common Intermediate Format): The default frame resolution of 352x288 for DVR systems is known as the CIF.

Coaxial Cable: A type of shielded cable capable of carrying a wide range of frequencies with very low signal loss.

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

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

Db (Decibel): A measure of the ratio of signal to noise. A camera should have a Db ratio of >46 for picture quality and the higher the number, the better.

DC Type Auto-Iris: Auto-iris lenses where the iris is controlled by the circuitry of the camera. See E.I. (Electronic Iris)

Decoders - A tool or program that deciphers encoded data into its original arrangement. The term is frequently utilized in mention to MPEG-2 video and sound data, which must be decoded before it can be produced.

Depth of Field: The regions in front of and behind the focused distance where the image remains in focus. With a greater the depth of field, more of the scene near to far is in focus. Lens aperture and scene lighting will greatly influence the D.O.F.

Digital: A signal with levels that are represented by the binary numbers 0 and 1.

Digital Recording: A recording of video received from one or more CCTV cameras. The video is recorded on a disk drive data on a PC.

Digital Video Monitoring System - Digital monitoring systems are video security systems that can be used with a VCR, DVR, or personal computer.

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

DVR (Digital Video Recorder): A device that receives images from several CCTV cameras at once and enables the images to be viewed on a monitor or recorded. A DVR is a device that records video to a hard disk in digital format.

DVR CCTV Recorder - DVR CCTV Recorders record actions on a surveillance camera on closed circuit television that can be used for later viewing.

Dwell Time: The length of time a switcher displays one camera before sequencing to the next, usually a variable setting.

E.I. (Electronic Iris) Shutter: Electronic Iris shuttering is the ability of the camera to compensate for moderate light changes in indoor applications without the use of auto iris lenses.

Electronic Surveillance System - Electronic Surveillance Systems can protect homes from break-ins, burglary, and assault. They can be in the form of burglar alarms that notify the police, security cameras, and closed circuit television systems

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

Extension Tubes: Various size spacers used between the camera and lens to reduce the Minimum Object Distance. Not recommended for use with zoom lenses due to the loss of tracking ability.

External Sync: The ability of CCTV equipment, normally cameras, to accept one or more of the standard sync formats so as to align itself to the rest of the system. Proper sync will prevent the monitor from “rolling” when switching the view from one camera to another.

F-Number: Indicates the brightness of the image formed by the lens, controlled by the iris. The smaller the F-number, the brighter the image will be.

F-Stop: A term used to indicate the speed of a lens. The smaller the F-number the greater amount of light passes through the lens.

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 of View: The horizontal or vertical scene size at a given length from the camera to the subject.

Flange Back: The distance from the flange of the lens (beginning of the lens mount) to the focal plane. C-mount lenses have a flange back distance of 17.526mm vs. 12.5mm for CS-mount.

Focal Length: The distance from the center of the lens to a plane at which point a sharp image of an object viewed at an infinite position. The focal length determines the size of the image and angle of field of view seen by the camera through the lens. This is the center of the lens to the image pickup device. The shorter the distance is, the wider the view; the longer the distance, the narrower (telephoto) the view.

Format: The size of the cameras pickup device (imager). Current standard formats are 1/4", 1/3" and 1/2".

Gen. Lock (See Ext. 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.

Gigabyte (GB):1,024 megabytes or 1 billion characters of information. Also see Megabyte.

Gray Scale: The number of variations from white to gray to black.

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

Ground Loop: Effects video pictures in the form of a black shadow bar across the screen or as tearing in the top corner of a picture. They are caused by different ground potentials in the system. The typically occur between the camera and the controls or monitor. This happens when both ends of a system are grounded.

H.264 Compression: The latest video compression technology, and is known as MPEG-4 part 10 (MPEG-4 AVC/H.264). See Video Compression.

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

Hunting: An industry term used to describe an auto-iris lenses inability to stabilize under certain light conditions.

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

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

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, an optical amplifier.

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

I.R. (Infra Red): A range of frequencies lower than visible red light used for covert and an additional light in low light surveillance. Active infrared illumination is a cost-effective technology for enabling truly effective 24/7 surveillance in any lighting conditions including total darkness, and the images produced are often mistaken for regular daytime monochrome images.

Iris: A mechanical diaphragm which can be controlled manually or automatically to adjust the lens aperture.

Lens Format: The size of a lens projected image. In most cases the lens will project an image slightly greater than the designated image size to insure the pickup device is completely covered. It is recommended that camera and lenses are the same format size. A lens with a larger format size can be used on a smaller format camera, however, a smaller format lens should never be used with a larger format camera.

Lens Speed: Refers to the lens aperture or its ability to transmit light. This is measured in F-stops.

Level Control: Used to set the auto-iris circuit to a video level desired by the user. Turning the level potentiometer towards the HIGH position will open the iris allowing more light to pass through the lens, towards the LOW will close the iris allowing less light to pass through the lens.

License Plate Reading: License plate reading requires specialized equipment in order to successfully overcome the challenges related to speed, lighting, reflectivity and headlight glare. Cameras chosen should be designed specifically for license plate reading as most conventional cameras will not work on a consistent basis. Infrared lighting is typically required for performance during both day and night.

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, or individual balanced video outputs for each video input. A looping DVR receives video from the camera, and each camera has an output from the DVR to connect anther recording or monitoring device.

Luminance (Y): The part of a video signal that consists of the monochrome data.

Lux: Specifications for surveillance cameras often include a minimum luminance level in lux at which the camera will record a satisfactory image. A camera with good low-light capability will have a lower lux rating.

The chart below summarizes the light levels occurring under daylight and typical low light level conditions. The equivalent metric measure of light level (lux) compared with the FC is given. One footcandle ≈ 10.764 lux and one lux = 0.3048² footcandle.

Light Condition	Lux	FC
Sunlight	107,639	10,000
Full Day Light	10,764	1,000
Overcast Day	1,076	100
Very Dark Day	107.64	10
Twilight	10.76	1
Deep Twilight	1.08	0.1
Full Moon	0.108	0.01
Quarter Moon	0.0108	0.001
Starlight	0.0011	0.0001
Overcast Night	0.0001	0.00001

Manual Iris Lens: A lens with a manual adjustment to set the iris opening (aperture) to a fixed position. This type lens is generally used in fixed lighting conditions.

Matrix Switch: A switch able to route any of its camera inputs to any of its monitor outputs; usually reserved for large systems, that often includes telemetry control.

Minimum Object Distance (M.O.D.): The closest distance a given lens will be able to focus upon an object. Generally, the smaller the focal length the shorter the Minimum Object Distance, this distance can be altered with use of extension tubes.

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 CCTV and television it is black and white

MPEG: A video compression codec, the latest version is H.262. See Video compression.

Noise: Undesired signal(s) that corrupts the original video signal and may reduce image quality.

Peak-To-Peak (P-P): 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.

Pinhole Lens: Lenses used primarily in covert applications where the camera/lens must remain out of sight. The Front of lens has a small opening to allow the lens to view an entire room through a small hole in a wall.

Pixel: Picture element. This is 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 will be.

Pre-Position Lenses: Pre-position lenses are specially designed lenses with extra mechanical/electrical components to allow for computer interfacing. This function allows the lens (when used with the appropriate controller) to feedback to the controller information relevant to zoom and focus propositioning allowing the controller to quickly scan to a pre-selected scene, arriving in focus at the proper zoom point without operator intervention.

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.

Quad: A device that compresses up to four video signals and simultaneously displays the images onto one monitor.

Rack Mount (19" Rack): An industrial standard housing 19" wide, its height is measured in units (U’s) of 1.75".

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, usually found in higher end, high security area, commercial DVRs.

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 needed.

Raster: The pattern of scanning lines upon which the picture is produced. The illuminated face of the monitor without the video information present is raster.

Reflected Light: The light reflected from a scene viewed by a camera. It has a direct impact on the video and ability to view details.

Remote Video Monitoring: Remote Video Monitoring (RVM) systems supply a method of automatically obtaining video information from isolated locations and transferring them to a central station workstation for processing.

Resolution: A measure of the ability of a camera, monitor 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 screen, usually seen when switching from one camera to another.

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

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.

Spot Filter: A neutral density filter paced at the center of one of the elements (or on an iris blade) to increase the high end of the F-stop range of the lens.

Super HAD CCD: Super HAD (Hole Accumulation Diode) CCDs allow more light to pass to each pixel, increasing sensitivity and reducing noise.

Switch or Switcher: A device used to switch the video signals from two or more cameras on a monitor

Sync: Abbreviation for synchronization. Electronic pulses inserted in a video signal for the purpose of assembling the picture information in the correct position on the monitor.

Tearing: This is a picture condition in which the horizontal lines are displaced in an irregular manner.

Telephoto: Telephoto is a term used to describe lenses that have a high focal number causing the reproduced image to appear larger than human eye reproduction.

Terminated (75 Ohm Terminated): For viewing and recording, a video signal must be terminated ate the last device in the circuit to maintain proper signal strength. Most CCTV equipment is self sensing / self terminating.

Tilt: The up and down tilting movement of a camera, to elevate or depress the vertical angle of view.

Time-Lapse VCR: Video recorder that can record frames with pauses between them thereby extending the time that a standard length tape will last.

Tracking: A zoom lenses ability to remain in focus throughout the entire zoom range.

Triplex: A multiplexer feature that gives you the ability to simultaneously view both playback and live cameras within the same multi-screen, while still encoding.

Vari-Focal: A lens with an adjustable focal length, designed to meet the need for versatility. This lens is set manually and is not controllable as an electronic zoom lens.

Video Compression: Video compression is a technology used to compress video to reduce video storage space and network transmission without sacrificing the video quality (not perfect but getting better). MPEG is the standard with the latest technology of the MPEG series H.264. For more detail see the Wikipedia entries:

Video Lens: An auto-iris lens with internal circuitry for processing of the video signal which controls the iris movements.

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.

Video Type Lens: An auto-iris lens using video signals to control the iris. All iris control voltages come from a circuit located within the camera.

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/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).

Zoom Lens: A lens with the ability to change its focal length manually or through the use of a controller to cover a variety of needs.

Zoom Ratio: The ratio of the starting focal length (wide) to the ending focal length (telephoto) of a zoom lens. A 10X zoom will magnify the image at the wide end by 10 times. Examples of a 10X zoom lenses; 8mm~80mm, 12mm~120mm.