L Terms

Lag: Synonymous with ghosting; image retained when an object moves in an under-lit scene, lag is a low-light phenomena usually associated with tube-type cameras.

LAN: Local area network

LASER: Stands for Light Amplification by Stimulated Emission of Radiation. A device that utilizes the natural oscillations of atoms or molecules between energy levels for generating coherent electromagnetic radiation in the form of light waves generally in the ultraviolet, visible or infra-red regions of the spectrum.

Laserdisc: See Videodisc.

Last Mile: The final connection to the consumers home. For local phone companies, the vast majority of their wiring is in the 'last mile' of network reaching the customer. Almost all of this wiring is twisted pair. This is the reason for the very high expense that will be required to upgrade phone networks to a broadband media such as coax or fiber.

LATA: Local access and transport area: Local phone calls are referred to as IntraLATA and long distance calls are InterLATA.

Latency: Signal delays introduced due to end-to-end signal processes (e.g. codec signal processing, protocol conversions etc.)

Layering: Making multiple recordings so as to place layers of graphics in a multi-element image.

LCD (Liquid Crystal Display): A technology used in flat panel display systems.

LCD Panel: A panel which allows text and graphics information from a personal computer to be displayed onto a large screen or wall using a standard transmissive-type overhead projector as the light source. It allows large groups of people to view the computer display and images at one time.

LD: Long distance.

LDC: Long distance carrier.

LDP: Laserdisc player, an electronic device which plays videodiscs.

LEC: Local exchange carrier: Provides local phone service and connection to long distance carriers.

Level: In MPEG, a level is a defined set of constraints on the values which may be taken by the parameters of this specification within a particular profile. A profile may contain one or more levels.

Level 1 Gateway: Video dialtone related term defined by the FCC. A telcos Level One Gateway service provides basic tariffed common carrier service (including transport, switching and interconnection) between a customer and a video programming service provider.

Level 2 Gateway: Video dialtone related term defined by the FCC. The Level Two Gateway is an optional telco video gateway offering enhanced services which are not subject to tariff regulation. A telco cannot provide their own video programming but they can determine which video programmers participate in their video dialtone gateway. Level Two Gateway may include premise equipment (e.g. set top box) as part of the service offering to customers.

Levels of Interactive Systems: Three degrees of videodisc system interactivity proposed by the Nebraska Videodisc Design/Production Group in 1980. They are: 1. Consumer model videodisc player- limited memory and processing power. 2. Industrial model with all the features of consumer model, plus on-board programmable memory and improved access time. 3. Qualities of 1. or 2. interfaced with an external computer and/or other peripheral processing devices.

Levels of Interactive Systems: A total integrated computerized system designed primarily for the storage, handling, and air-play of broadcast commercial segments. The LMS controls all devices, including the multi-cassette system and any external VTRs and peripherals, through a system application controller .

Limited Motion Codec: A picture processor or codec which takes full motion video information and reduces it to a series of video snapshots to be transmitted at a low data rate between sites. Does not include codecs which convey full motion video.

Limiter: A type of compressor that restricts output from exceeding a preset level.

Line Pairs: A measure of resolution often used in film and print media. There is often confusion when comparing film and video lines of resolution. In film, line pairs are measured as the number of line transitions measured per millimeter or per inch. Vertical resolution is measured with horizontal lines. Horizontal resolution is measured with vertical lines (see Resolution). Diagonal resolution is measured with diagonal lines. In video, lines of resolution are a measure of the maximum number of line transitions perceived over the entire length or width of the picture screen.

Linear: A motion video or film sequence designed to be played from beginning to end without stops or branching. Linear usually refers to traditional video or films which are meant to be watched by the viewer passively from beginning to end without interaction.

Linear Video: Any video program which plays from start to finish with no variation in sequence or pace of information presented.

Link: A communications channel which ties together only two sites. A network is made up of many links.

Live: Television that is transmitted as the event occurs.

Local loop: Telecom circuit providing connectivity between telephone subscriber and the local Local subscriber loop central office switching center.

Longitudinal Recording: This process of running the tape past a stationary head in a longitudinal and linear fashion.

Longitudinal Time Code: Code recorded on one of the audio channels or on the address track.

Looping: A video device (switcher, monitor, etc.) that allows video inputs to pass through outputs to other devices without terminating. By looping the signal through a device, one signal can drive several devices.

Lossless: Image and data compression applications and algorithms which reduce the stored size of a data or graphic file without losing critical data.

Lossy: Methods of image compression, such as JPEG, that reduce the size of an image by eliminating some pictorial information. Lossy methods result in some image degradation which is usually a factor of the degree of compression. The greater the compression ratio (more information removed), the more image degradation. .

Low-Pass Filter: A special circuit used in a variety of audio systems, including microphones and mixers, that blocks high frequencies.

Lumen: A measurement of light emitted by a light source at the point of emission.

Luminance: Amplitude (brightness) of the gray scale portion of the television signal. The Y signal. The range of brightness from black through gray to white in a video picture.

Lux: The metric measurement of light intensity taken at the surface which the light source is illuminating. The measure of the total lumens falling upon a unit of area. 1 lumen per square meter. One footcandle equals 10.76 lux.