Detailed Security System & Fire Alarm Definitions
Quick Reference Security Systems Definitions
Fire Alarms & Accessories Definitions
Door Access Control Definitions
Closed Circuit Television CCTV Definitions
Phone Systems Definitions


Activity Detection - A feature commonly used in multiplexors to improve update times in cameras and give relay closures.

Angle of View - The focusable range within the image size. The larger the focal length, the smaller the angle of view. The smaller the focal length, the wider the angle of view.

Aperture - Usually controlled by a electronic iris, the aperture controls the amount of light allowed inside the camera. The larger the F-Stop number the less light.

Alarming - A preprogrammed response to a input signal from a contact closure. The response may vary depending on the type of equipment.

Aspect Ratio - The ratio between the height of the picture frame and the width.

Automatic Frequency Control - A electronic circuit that automatically regulates the oscillator to within specified parameters.

Automatic Gain Control - A electronic circuit that automatically regulates the gain of a signal due to a input or within specified parameters.

Automatic Iris Lens - A lens that automatically opens or closes the aperture in order to maintain proper light levels.

Automatic Level Control - A feature that allows auto iris lenses to bring out detail in bright areas or in dark areas depending on how it is adjusted.

Auto Terminating - A feature allowing the monitor to automatically select correct termination depending on if the video output is connected.

Auto White Balance - A feature that allows a color camera to automatically adjust its color to sharpen white areas within the picture.

Attenuation - A signal loss or decrease.

Back Focal Distance - The distance between the image plane and the rear most portion of the lens.

Back Light Compensation - A feature that automatically compensates for high background light in order to give better detail to darker areas of the picture.

Bridging - A term usually used with switchers meaning that a high impedance video line is paralleled to a source of video.

"C" Mount - A type of lens mount that has a flange back distance of 17.5mm. "C" mount lenses have a longer back focal distance than "CS" mount lenses.

"CS" Mount - A type of lens mount that has a flange back distance of 12.5mm. "CS" mount lenses have a shorter back focal distance than "C" mount lenses.

Charged Coupled Device (CCD) - An image sensor which is a large scale integrated circuit containing hundreds of thousands of photo-sites (pixels) which convert energy to electronic signals.

Conditional Refresh - A feature frequently used in transmission equipment that only transmits small changes within the picture. The full picture is transmitted only after a larger percentage changes within the picture.

Coaxial Cable - A particular type of cable designed to transmit a large range of frequencies with loss signal loss.

Composite Video - A video signal that combines the picture signal, synchronizing pulses and vertical and horizontal blanking.

Crosstalk - An unwanted signal that interferes with the video signal.

DC Type Lens - A auto iris lens that receives video signals and voltage from the camera to adjust the iris.

Depth of Field - The area in front of the camera, measured front to back, which is in focus.

Digital - A signal with binary numbers representing the levels.

Dwell Time - A feature on switchers that determines how long each camera is held before switching to the next camera.

Electronic Iris - A feature which automatically adjust the camera's shutter to account for lighting changes. In some cases eliminating the need for an auto iris lens.

F-Number - A number indicating the brightness of the image and controlled by the iris. The smaller the f-number, the brighter the image.

F-Stop - A term indicating the speed of the lens. The smaller the f-number, the greater the amount of light allowed to pass through the lens.

Field - Part of a frame consisting of either the horizontal or vertical lines of resolution. 60 frames per second equals 30 frames per second.

Focal Length - The distance from the center of the lens to an object at a infinite distance from the camera that comes into focus.

Footcandle - The light intensity of a object one foot away from a one candela source.

Frame - A complete picture consisting of horizontal and vertical lines.

Ghost - An image with a shadow or weak picture. Ghosts are commonly caused by poor transmission means in which secondary signals are received either before or after the primary signal.

Horizontal Resolution - The number of picture elements with a single scanning line.

Image Size - The size of an image formed by the lens onto the chip or pickup device. These sizes are referred to as 1/4", 1/3", 1/2", 2/3" and 1" being measured diagonally.

Incident Light - How much light that is on an object.

Level Control - An iris control used to set the circuit within the auto-iris to a desired video level. A higher setting will let more light in and a lower setting will close the iris therefor allowing less light in.

Line Lock - The ability to synchronize AC powered cameras to the same line voltage frequency.

Looping - A term used when a high impedance device has been permanently connected in parallel to a video source.

Lux - A unit of measure used to determine the intensity of a lightsource.

Manual Iris Lens - A lens that is manually adjusted to open or close the aperture according to the lighting conditions.

Matrix Switcher - A type of switcher with the ability to send any incoming video signals to any of its video outputs.

Modulate - The changing of the parameter of a video signal's frequency or amplitude.

Monitor - A device which displays video signals to be view by the user..

Monochrome - A black and white signal or picture.

Multiplexor (Simplex) - A device that very quickly switches between cameras therefore reducing the dwell time on each camera as is normally associated with conventional switchers. Cameras can be viewed on screen one at a time or multiple. Simplex multiplexors record only what is being viewed on the screen by the user.

Multiplexor (Duplex) - Same as above except duplex multiplexors record all cameras regardless of what the user views on the screen.

Peak to Peak - A term referring to the different amplitudes between the most positive and most negative excursions of a signal.

Pinhole Lens - A type of lens commonly used with hidden cameras.

Pixel - The microscopic photo-sensitive sites on a CCD image sensor

Quad - A device which display's up to four cameras on the monitor's screen at once.

Resolution - A term used to measure a cameras picture elements and how those elements are reproduced.

Roll - The loss of vertical synchronization which causes the picture to move up or down on the monitor's screen.

Saturation - The amplitude of the chrominance signal effecting the vividness of a color.

Screen Splitter - A device which displays two cameras on the monitor's screen at once.

Sensitivity - A term referring to the amount of current developed per unit of incident light. It is measured in footcandles.

Signal to Noise Ratio - The ratio between a useful video signal and unwanted noise.

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

Switcher - A device which either automatically switches or manually switches between user selected cameras. The dwell time, the time spent on each camera, can also be adjusted by the user.

Synchronization - Electronic pluses that are inserted into the video signal in order to assemble the picture correctly.

Time-Lapse Recorder - A video recording device that slows down the rate at which images are recorded. The recording speed can be set to record up to 960 hours onto a normal VHS tape. The longer the recording speed, the chopper the image.

Tracking - The ability of a zoom lens to remain is focus from wide-angle to telephoto positions.

Video Motion Detector - A device that analyzes the pixels within a video signal from a camera to determine if there is movement within the picture.

Video Type Lens - An auto-iris lens without the internal circuit that controls the iris. The lens relies on signals from the camera.

Zoom Lens - A lens with the ability to adjust the focal length from wide angle to telephoto.