ADTRAN Atlas 550 - Manual (Page 247)

Appendix G. Glossary
61200305L1-1 ATLAS 550 User Manual G-7
µµµµ
-Law
A companding standard for converting between analog and digital in a PCM system.
µ
-Law is mainly
used in North America. A-Law is the European equivalent.
multiplexer
A device (mux) that takes several low-speed channels and merges them into one high-speed channel
at one end of a link. Another multiplexer at the other end of the link reverses this process.
N391
Defines how many link integrity polls occur before a full status poll. One out of the number defined in
N391 is a full status poll. Default is 6.
N392
Defines how many bad polls can occur within an N393 window before the link is declared down.
N393
Defines the number of polls that make up the window used by N392 to determine if a link is opera-
tional.
NNI
A standard interface between two frame relay switches.
nonvolatile memory
Any form of memory that retains its contents when power is removed (for example, ROM, EPROM,
etc.)
NT1
Network termination 1. A unit that provides physical and electromagnetic termination of the U-inter-
face, 2-wire transmission line; converts between Layer 1 formats used at the U- and T- reference points;
and performs some maintenance functions.
Octal FXO Module
One of the ATLAS 550 option modules. The Octal FXO provides eight analog interface to a system or
PBX.
Octal FXS Module
One of the ATLAS 550 option modules. The Octal FXS provides eight 2-wire interface that can operate
in the PLAR, Tandem, or FXS mode to provide analog voice.
option modules
Any optional, hot-swappable module that can be added to the ATLAS 550 system for a variety of
applications.
OSI
Open System Interconnection. It is a standard defined by ISO and the ITU-T to allow interoperability
between equipment of different vendors.
overbooking
ATLAS 550 feature that reduces telecommunications expenses by allowing you to over-subscribe
switched bandwidth for situations where simultaneous access to the network by every subscriber is
not required.
Packet
A transmission that contains both control information and data.