Surveillance Equipment Definitions

Listed below is a list of terms and abbreviations commonly used with video surveillance equipment.  This is only a partial list, but as questions arise regarding equipment and terms, we will include them in this page.

AGC - Automatic Gain Control  is an electronic system found in many types of devices.  Its purpose is to control the gain of a system in order to maintain adequate performance over a range of input signal levels.  Or an electronic circuit that tries to keep the video signal at a constant level (1volt peak-peak).  Useful on cameras working at low light levels.

AI - Auto Iris  is an electronic circuit that acts as an iris on CCD cameras by electronically shuttering the CCD sensor.  Or an automatic method of varying the size of a lens opening in response to changes in scene illumination.

AWB - Auto White Balance  is an electronic process used in video cameras to retain true colors.  It is performed electronically on the basis of a white object in the picture.

CCD - Charged Coupled Device  is an analog technology that uses 12 volts instead of the 9 volts used by CMOS cameras.  The CCD camera has a slightly better picture resolution than CMOS cameras, as well as functions better in low light situations.  Drawbacks are that a CCD camera drains more power than a CMOS camera and is generally larger in size.  CMOS cameras are smaller than CCD cameras and operate longer on with the smaller 9 volt battery.

CMOS - Complementary Metal Oxide Semiconductor  is a lower resolution camera compared to CCD models, but operates at lower current.

HAD CCD - Hole Accumulation Diode  is a type of CCD sensor with a layer designed to accumulate holes (in the electronic sense), thus reducing a pictures noise level.

S to N Ration - Signal To Noise Ratio  is simply the ratio of the signal power and noise power, expressed in decibels (dB).  Or the measure of noise on a video signal.  It is represented in Decibels as the level of the video signal compared to the level of noise present on that signal.  The higher the signal to noise ratio the better.

BLC - Balance Light Control  is a method to compensate for bright spots in a picture.  It is also important to consider whether there are bright spots in the picture such as car headlights which can make identification of the vehicle registration or model impossible.  This can also be a major problem where it is necessary to identify a person who is moving from bright daylight into artificial light.  This could result in the subject becoming an unidentifiable silhouette.

OSD - On Screen Display  is a method of displaying set-up information or instructions on to a display monitor.

Resolution - Resolution  measures the cameras ability to reproduce an image.  The higher the resolution, the better the picture quality.

LUX - Lux  is the Illumination equal to a luminous flux of 1 lumen per square metre.  1 lux is equivalent to 0.0929 foot-candle. (Symbol lx)

FPS - Frames Per Second  is the number of still frames (pictures) that give the illusion of motion, which appear in a single second of time.  30 fps is considered "Real Time".  So for real time viewing of your camera, you need at least 30 fps for each camera.

IR -  Infrared  is the part of the electromagnetic spectrum with a longer wavelength than light but a shorter wavelength than radio waves.  IR LEDS are commonly used on day/night cameras which allow the camera to see in the dark.

Focal Length - Focal Length  is the distance from the surface of a lens and its focal point.

Focal Point - Focal Point  is the axis of a lens or mirror to which parallel rays of light converge or from which they appear to diverge after refraction or reflection.