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.