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To use the glossary, simply click on the first letter of
the term of interest below:
L
- LAN
- Local Area Network, usually used to connect workstations to a server or to each other, operating at modest speeds. Ethernet, available at 10-, 100- or 1000-Mbps is perhaps most widely used. In general, LANs do not provide guaranteed bandwith to users and may have significant latency depending upon system loading. Consequently, their use with VoIP and videoconferencing may be problematic.
- LAP
- Link Access Protocol (frame relay use, LAPD)
- LATA
- Local Access and Transport Area, a telecommunications tariff
aspect in the USA.
- Latency
- The amount of delay in a LAN or WAN. For basic data where a
small delay can be tolerated, latency is usually not an issue. However, for
communications services used for videoconferencing or VoIP for example, latency
can interfere with the audio and/or visual communications. In shared bandwidth
transmission environments, it is possible to encounter latency which varies
dynamically, caused by perhaps a single user accessing or originating
multi-megabyte-sized files or accessing high bandwidth streaming signals.
- LCD
- Liquid Crystal Display. A very low-power device capable of
displaying characters, words and symbols, often built into a telecommunications
equipment control panels.
- LCP
- Link Control Protocol (PPP usage)
- LCR
- Least-Cost Routing.
- LDAP
- Lightweight Directory Access Protocol, developed at
the University of Michigan as a front-end to the more complex ITU-T X.500
directory protocol, formalized in 1995 in RFC 1777. It includes five models:
data, organization, security, function and topology. It is useful for a wide
range of uses including simple dialing directories and indexing large databases.
- LEC
- Local Exchange Carrier
- LEO
- Low Earth Orbit, non-geosynchronous satellites used
for communications and other purposes.
- Lip Sync
- The maintenance of sound (i.e., speech) exactly in step with
movement in a visual image (e.g., talking heads). A common cause is different transmission paths and transmission technologies for the sound and image signals.
Within codec hardware, the processing time for the video portion of the signal is about 100 times longer than the audio processing time. Consequently, codecs usually incorporate adjustable audio delay circuitry to delay-equalize the two signals to maintain lip sync.
- LMCS
- Local Multipoint Communication System, another version of MMDS or "wireless cable TV"; a term used in Canada. Data rates can be as high as 155 Mbps compared to 64 Kbps cell phones and, depending on jurisdiction, may operate between 2-GHz and 42-GHz with up to 3-GHz of spectrum available.
- LMDS
- Local Multipoint Distribution Service, a
broader-band, higher frequency, version of MMDS or "wireless cable TV". Data rates can be as high as 155 Mbps compared to 64 Kbps cell phones and, depending on jurisdiction, may operate between 2-GHz and 42-GHz with up to 3-GHz of spectrum available.
- LMR
- Land Mobile Radio
- LMSS
- Land Mobile Satellite Service
- LNA
- Low Noise Amplifier, an active device usually used in conjunction with an appropriate antenna to amplify and receive satellite microwave signals.
- LNB or LNBC
- Low Noise Block Converter, an active device used in
conjunction with an appropriate antenna to convert a range of satellite signals
to some intermediate frequency for processing by a receiver etc.
- Loop Filter
- H.261, H.263 video compression algorithm usage. See Spatial Filtering.
- Luminance
- The portion of a composite video signal that represents the monochrome or brightness part of the image.
- LZW
- Lempel-Ziv-Welch; a lossless data compression algorithm named after its developers.
To use the glossary, click on the first letter of
the term of interest:
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