Glossary and Abbreviations

555-230-024GL-30 Issue 5 January 1998

line port
Hardware that provides the access point to a communicatio ns sy s tem for eac h ci rcu it a ss oci ate d
with a telephone or data terminal.
link
A transmitter-receiver channel that connects two systems.
link-access procedure on the D-channel (LAPD)
A link-layer protocol on the ISDN-BRI and ISDN-PRI data-link layer (level 2). LAPD provides data
transfer between two devices, and error and flow control on multiple logical links. LAPD is used
for signaling and low-speed packet data (X.25 and mode 3) on the si gna lin g (D-) channel and for
mode-3 data communications on a bearer (B-) channel.
LINL
Local indirect neighbor link
local area network (LAN)
A networking arrangement designed for a limited geographi cal area . Generally , a LAN is limi ted in
range to a maximum of 6.2 miles and pr ovides high-speed carrier servi c e with low error rates.
Common configurations include daisy chain, star (including circuit-switched), ring, and bus.
logical link
The communications path between a processor and a BRI terminal.
loop-start trunk
A trunk on which, after establishing a connection with a distant switching system for an outgoing
call, the system waits for a signal on the loop formed by the trunk leads before sending the digits
of the called number.
LSU
Local storage unit
LWC
Leave Word Calling
M
MAC
Medium access
MADU
Modular asynchronous data unit
main distribution frame (MDF)
A device that mounts to the wall inside the system equipment room. The MDF provides a
connection point from outside telephone lines to the PBX switch and to the inside telephone
stations.
main-satellite-tributary
A private network configuration that can either stand alone or access an ETN. A main switch
provides interconnection, via tie trunks, with one or more subtendin g switches, cal led satellites; all
attendant positions for the main/satellite configuration; and access to and from the public
network. To a user outside the complex, a main/satellite configuration appears as on e switch, with