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Issue 2 - 07/00 A4-7
Appendix 4—Glossary & Abbreviations
LCD
A Liquid Crystal Display, such as the screen on aurora
Sonata
.
LE
An exchange which is local to subscribers and into which
their lines terminate.
LED
Light Emitting Diode.
Loopback
Data received on the Rx channel of a circuit is
retransmitted on the Tx channel of the same circuit.
Master clock
The clock which acts as a prime source within a network
and from which all other clocks derive their
synchronisation.
Modem
A device which converts digital signals into analogue tones
which can be passed through the telephone network. A
modem at the receiving end reverses this process to
recreate the original digital signal.
Monitoring
A mode of operation where an aurora tester is set to
receive information about current activity from ISDN
equipment, i.e. an NT, TE or another aurora tester. The
tester is only used to receive information, not to transmit.
MSN
Multiple Subscriber Number.
μ-law
A companding technique used for PCM systems in North
America, Japan and some other regions in Asia.
Multiframe
A set of consecutive frames, used in digital transmission, in
which the position of each frame can be determined by a
multi-frame alignment signal covering the group of frames.
Multiplexing
The process of enabling several users to share the same
communication channel.
NFAS
Non Frame Alignment Signal (PRT or North America:
Non Facility Associated Signal)
National
A standardised ISDN protocol used in North America.
ISDN
Also referred to as NI.
Node
A point where one or more functional units interconnect
transmission lines.