ADTRAN 550 user manual Nni

Appendix G. Glossary

∝-Law

A companding standard for converting between analog and digital in a PCM system. ∝ -Law is mainly used in North America. A-Law is the European equivalent.

multiplexer

Adevice (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.

61200305L1-1 ATLAS 550 User Manual G-7