LAN : An acronym for Local Area Network. This could be as small as a two computer system, or, it could incorporate hundreds of users in a campus environment. It is local in that there is a direct wire connection between all parts of the network.
LCD : Liquid Crystal Display. An LCD is a flat-screen slim profile video display.
LED : A LED is a Light Emitting Diode.
Legacy : This term refers to existing products in the field. Some disappear quickly and some hang on seemingly forever. Manufacturers typically use the term to identify previously sold and now discontinued products that they are still obligated to service and support.
Level of Service : This is the degree of effort applied to the manufacturer’s service capability as measured in funding budget, number of service personnel, equipment, training etc.
Levels of Support: This refers to the individual levels of support functions in an organization. The terminology varies from company to company. The basic idea is this: Level #1 is the service tech at a customer site. Level #2 is whoever he calls for help. Level #3 is whoever Level #2 calls etc. Eventually the level reaches to the engineering development group.
Line locked : The sync pulses of cameras are locked to the AC mains frequency (50/60 Hz).
Line Powered Camera : A camera in which the power is supplied along the same coaxial cable that carries the video signal. This was once common before digital devices showed up in CCTV. The DC offset may destroy a DVR or MUX (multiplexer).
Linked alarms : Allow one alarm to trigger another. An example is an alarm on one camera may be configured to move another PTZ camera to a preset position.
Live Video : Live displays current activity. This can be at the camera location or at a remote site connected to the cameras through the Internet.
Loop Out : This term refers to the additional BNC connectors installed for the purpose connecting the incoming video to additional devices. You will see these installed on many CCTV products.
Luminance : Brightness. This is the black and white portion of the composite video signal. See Chrominance.