Broadband Cable Association of Pennsylvania

Glossary - L

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Laser - A device that generates coherent electromagnetic radiation in, or near, the visible part of the spectrum.

Last Mile Framing - The data encapsulation and transmission protocols used between the consumer premises and the headend. Framing techniques include ATM, MPEG and IP.

Latency - The time, expressed in quantity of symbols, taken for a signal element to pass through a device.

Layer - In networks, layers refer to software protocol levels comprising the architecture, with each layer performing functions for the layers above it.

Leapfrogging - Cable television operators' practice of skipping over one or more of the nearest TV stations to bring in a further signal for more program diversity. FCC rules establish priority for carrying stations that lie outside the cable systems service area.

Leaseback - The practice by telephone companies of installing and maintaining cable television distribution systems, and leasing the facilities back to separate contractors for operation of the system.

Leased Access - On some systems, a public access channel for which programmers pay a fee for use and are permitted to sell commercial time in their programming. Also known as Leased Channel.

Line Frequency - The number of horizontal scans per second, nominally 15,750 times per second.

Line Speed - The rate at which individual bits are transmitted on a telephone connection. A modem's line speed may be set at 14,400 bits per second, an ISDN line at 64,000 bits per second. Line speed does not take into account whether the data it is sending has been compressed to increase actual Throughput.

Local Access and Transport Area (LATA) - A geographical area used for regulatory, pricing, and network organization purposes to partition the public switched telephone network into distinct regions.

Local Area Network (LAN) - A LAN is a collection of computing equipment at a single location (e.g., an office building or campus) that communicate with each other to share resources and information, such as disk storage and files, printers, and email. See also WAN.

Local Distribution System (LDS) - A wide band microwave system or cable system which is capable of transporting a number of television signals simultaneously. Used to interconnect cable system headends.

Local Exchange - An exchange where telephone subscriber lines connect.

Local Exchange Carrier (LEC) - Telephone company lingo for your local telephone company. See also RBOC.

Local Loop - This portion of the telecommunications network physically connects end users to the central office network facilities and generally is dedicated to that particular user. Twisted pairs of copper wire form the traditional medium of the telephone network local loop, although other connections now are used in some cases.

Local Number Portability (LNP) - A system that allows local telephone numbers to be transferred to competitive local exchange carriers. This allows the subscriber to change local phone companies without experiencing a change in phone numbers.

Local Origination - Programming developed by an individual cable TV system specifically for the community it serves.

Local Signals - Television signals that are received at locations that are within the station's Predicted Grade B Contour. Cable systems must carry all commercial local signals in their areas.

Logical Link Control (LLC) procedure - In a local area network (LAN) or a metropolitan area network (MAN), that part of the protocol that governs the assembling of data link layer frames and their exchange between data stations, independent of how the transmission medium is shared.

Low Band - TV channels 2 through 6.

Low Noise Amplifier (LNA) - A low noise signal booster used to amplify the weak signals received on a satellite antenna. Usually found in the receiver front ends.

Low Power Television - Broadcast medium that is similar to commercial TV but limited in broadcast coverage area by its low power signal.

Low Split - When upstream frequencies are assigned below 54Mhz.

Low VHF Band - The part of the frequency band allocated by the FCC for VHF broadcast television, including television channels 2 through 6, or 54 through 108 MHz.

Luminance Signal - That portion of the NTSC color television signal which contains the luminance or brightness information.

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