Sun Surveillance, wireless solar powered video surveillance, glossary l

The Glossary

An all inclusive glossary of security lingo is provided for your convenience. This list
will undoubtedly be helpful when delving in to the realm of security.

L:

Lambertian source or surface - A surface is called a Lambert radiator or reflector (depending whether the
surface is a primary or a secondary source of light) if it is a perfectly diffusing surface.
LAN - Local Area Network. A short distance data communications network (typically within a building or
campus) used to link together computers and peripheral devices (such as printers, CD ROMs and
modems) under some form of standard control.
Laser - Light amplification by stimulated emission of radiation. A laser produces a very strong and
coherent light of a single frequency.
LED - Light Emitting Diode. A semiconductor that produces light when a certain low voltage is applied to it
in one direction.
Lens - An optical device for focusing a desired scene onto the imaging device in a CCTV camera.
Level - When relating to a video signal it refers to the video level in volts. In CCTV optics, it refers to the auto
iris level setting of the electronics that processes the video signal in order to open or close the iris.
Line-locked - In CCTV, this usually refers to multiple cameras being powered by a common alternative
current (AC) source (either 24 V AC, 110 V AC or 240 V AC) and consequently have field frequencies locked
to the same AC source frequency (50 Hz in CCIR systems and 60 Hz in EIA systems).
Liquid crystal display (LCD) - A screen for displaying text/graphics based on a technology called liquid
crystal, where minute currents change the reflectiveness or transparency of the screen. The advantages of
LCD screens are very small power consumption (can be easily battery driven) and low price of
mass-produced units. The disadvantages are narrow viewing angle, slow response (a bit too slow to be
used for video), invisibility in the dark unless the display is back lighted, and difficulties displaying true
colors with color LCD displays.
Lumen [lm] - A light intensity produced by the luminosity of 1 candela in one radian of a solid angle.
Luminance - Refers to the video signal information about the scene brightness. The measurable,
luminous intensity of a video signal. Differentiated from brightness in that the latter is non-measurable and
sensory. The color video picture information contains two components, luminance (brightness and
contrast) and chrominance (hue and saturation). The photometric quantity of light radiation.
LUT - Look-up table. A cross-reference table in the computer memory that transforms raw information from
the scanner or computer and corrects values to compensate for weakness in equipment or for differences
in emulsion types.
Lux [lx] - Light unit for measuring illumination. It is defined as the illumination of a surface when luminous
flux of 1 lumen falls on an area of 1 m2. It is also known as lumen per square meter, or meter-candelas.

Courtesy of CCTV Labs and CCTV focus magazine

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