Command Reference Guide

206 ● pcm 3Com Router 5000 Family and Router 6000 Family
Command Reference
pcm
Purpose Use the pcm command to configure a companding law used for quantizing signals.
Use the undo pcm command to restore the default.
Syntax pcm { a-law | µ-law }
undo pcm
Parameters a-law
Companding A-law, used in most part of the world,
such as China, Europe, Africa, and South America.
µ-law
Companding µ-law, used in North America.
Default By default, A-law applies.
Example Adopt µ-law companding for signal quantization.
[Router-voice-line3/0/0:0] pcm u-law
View This command can be used in the following views:
■ Voice Subscriber-Line view
Description Companding laws are usually adopted to quantize signals unevenly for the purpose of
reducing noise and improving signal to noise ratio. Underpinning this approach is the
statistics about voice signals, which indicate that lower power signals are more likely
present than high power signals.
According to CCITT, when two countries use different companding schemes
communicate, the side using µ-law is responsible for converting signals to A-law.