MERLIN LEGEND Communications System Release 6.0
System Programming
555-660-111 Issue 1
February 1998
Glossary
PageGL-17
L
LAN (local area network) Arrangement of interconnected
personal computers or terminals, sometimes accessing a
host computer, sometimes sharing resources such as files
and printers.
LDN (Listed Directory Number)
LED (light-emitting diode) Semiconductor device that produces
light when voltage is applied; light on a telephone.
line Connection between extensions within the
communications system; often, however, used
synonymously with

trunk

.
line and trunk
assignment Assignment of lines and trunks connected to the system
control unit to specific buttons on each telephone.
line coding Pattern that data assumes as it is transmitted over a
communications channel.
line compensation Adjustment for the amount of cable loss in decibels (dB),
based on the length of cable between a 100D module a nd
a channel service unit (

CSU

) or other far-end connection
point.
line/trunk Refers to inside system lines and outside lines/trunks in
general terms. See also

line

and

trunk

.
line/trunk jack Physical interface on a module in the control unit for
connecting an outside line/trunk to the communications
system. Also called “trunk jack.”
line/trunk and
extension module Module on which the jacks for connecting central office
lines/trunks and/or the jacks for connecting the extensions
are located.
local dial plan In a system that is part of a
private network
, a list of
extension ranges that the local system references in order
to route local

intersystem calls via UDP

.
local host
computer access A method for connecting an extension jack to an on-site
computer for data-only calls through a
modem
or

ISDN

terminal adapter

.
local loop The two-way connection between a customer’s premises
and the central office (CO).
local user In a
private network
, a person whose extension is
connected to the local control unit.
logical ID Unique numeric identifier for each
extension
and

line/trunk

jack

in the system control unit.
loop-start line Line on which a closure between the tip an d ring leads is
used to originate or answer a call. High-voltage 20-Hz AC
ringing current from the central office signals an incoming
call.