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LAN

Local Area Network; a network that connects users residing in relatively close physical proximity to a single physical network.

LAPD

See Link Access Procedures on the D Channel (LAPD).

LAPD stack mode

An AG ISDN protocol stack mode in which the protocol stack implements layer 2 functionality only. No channelizer or ACU is present. The application communicates directly with the data link layer. See also ACU stack mode, NCC stack mode.

latency

The delay between the time that data is sent from its origin and the time it is received at its destination.

layer

In the OSI seven-layer protocol model, a level of digital communication. Each layer generally has one or more protocols associated with it. Communication networks for computers can be organized as a set of independent protocols, each in a different layer (or level). The lowest layer governs direct host-to-host communication between the hardware at different hosts; the highest layer consists of user applications. For each layer, programs at different hosts use protocols appropriate to the layer to communicate with each other. See also ACU stack mode, data link layer, end-to-end layers, LAPD stack mode, NCC stack mode, network layer, physical layer.

LE

Local Exchange equipment; an ISDN equipment category.

left clocks

MC1 clock signals driven by the primary or secondary clock master. See also primary [clock] master, right clocks, secondary [clock] master.

Letter-to-Sound Module (LSM)

A software module in NaturalText that converts ASCII text into data the format synthesizer can use to produce synthesized speech. The LSM uses linguistic and phonetic rules to map letters and syllables to appropriate sounds.

life cycle functions

Service manager binding functions which perform service registration, event initialization and shutdown, and service initialization and shutdown.

line

A logical telephone connection on which a call can take place.

line seizure

The process by which a switch or station instrument (phone) takes control of a telephone circuit.

Link Access Procedures on the D Channel (LAPD)

CCITT recommendation Q.921; a protocol for communication at the data link layer. See also data link layer.

listener(s)

In the CT Access Point-to-Point Switching service, the timeslot(s) that receives input from a connection. See also connection, talker.

local area network

See LAN.

local loop

The voice-band channel connecting the subscriber to the central office (CO).

logical port

See virtual port.

loopback

A local connection between the input and output of a device. This is typically used for testing purposes.

loop start (LS)

A method of signaling an off-hook or a line seizure, where one end of the connection closes the loop circuit and the resulting current flow is detected by the switch at the other end.