Table of Contents
Advertisement
GLOSSARY
Leased Line
LED
Line Code Violation
Event
Link
Loopback
Loss of Signal (LOS)
Master CSU
M o d e m
Multiplex
Multiplexed Channel
Multiplexer
Multiplexing
M u x
Network
B-6
the CSU transmit a keep alive signal when conditions are such that a normal
data stream cannot be transmitted.
A dedicated circuit, typically supplied by the telephone company, that permanently
connects two or more user locations; generally voice-grade in capacity and in
range of frequencies supported; typically analog, though sometimes refers to DDS
subrate digital channels (2.4 to 9.6 kbps); used for voice (2000 Series leased line)
or data (3002-type); point-to-point or multipoint; may be enhanced with line condi-
tioning; also private line.
Light-emitting diode.
For an AMI-coded signal, this is the occurrence of a received bipolar violation.
For a B8ZS-coded signal, it is the occurrence of a received bipolar violation that is
not part of the associated zero-substitution code.
The combination of communications devices, media and software intelligence
that is required to effect data communications.
Diagnostic procedure used for transmission devices; a test message is sent to a
device being tested, which is then sent back to the originator and compared with
the original transmission; loopback testing may be within a locally attached de-
vice or conducted remotely over a communications circuit.
An LOS condition occurs when the CSU senses an absence of signal from either
side for more than 150 milliseconds when in the AT&T mode, or 175 bit periods
when in the ANSI mode. A network signal with loss greater than 28.5 dB is con-
sidered no signal, while an equipment signal with excessive consecutive zeros is
considered no signal. In response to receiving an LOS from one side, the CSU re-
turns a Yellow alarm, and transmits an AIS to the other side.
A DataComm 551 option that allows configuration of the CSU through the Supervi-
sory terminal.
Modulator/demodulator; electronic device that enables digital data to be sent over
(typically) analog transmission facilities.
The interleaving of message elements (bits and characters) from a variety of
data sources into one or more combined signals.
A communications channel capable of servicing a number of devices, or users, at
a time.
Any multiport device that allows two or more users to share a common physical
transmission medium; employed in pairs, one at each end of the communications
channel, where each device performs both multiplexing of the multiple user inputs
and demultiplexing of the channel back into the separate user data streams.
The combining of multiple data channels onto a single transmission medium;
any process through which a circuit normally dedicated to a single user can be
shared by multiple users; typically, user data streams are interleaved on a bit or
byte basis (time division) or separated by different carrier frequencies
division).
Multiplexer.
An interconnected group of nodes; a series of points, nodes, or stations connected
by communications channels; the assembly of equipment through which connec-
tions are made between data stations.
(frequency
Advertisement
Table of Contents
