3Com NBX 100 Administrator's Manual - page 261
System Settings
261
System-wide Audio
Compression
Select one of these compressions settings as the default
setting for all calls:
None - G711 — No compression, G.711 (MULAW) audio
encoding
Med - ADPCM — Medium compression, ADPCM audio
encoding
High - G729 — High compression, G.729 audio encoding.
You can override the system wide setting for individual
telephones, line card ports or T1/E1 spans (3C10116D and
3C10165D only).
Audio Compression
on VTL Calls
Select one of these compressions settings as the default
setting for calls over virtual tie lines:
None - G711 — No compression, G.711 (MULAW) audio
encoding
Med - ADPCM — Medium compression, ADPCM audio
encoding
High - G729 — High compression, G.729 audio encoding.
Echo Troubleshooting controls can reduce or eliminate audio feedback (echo)
during conversations. The NBX system has default mechanisms to deal with echo,
however, extreme conditions can induce echo that is beyond the scope of the
default mechanisms.
NOTE: When additional echo suppression is enabled for analog and digital line
cards, echo should be reduced or eliminated. However, in rare conditions, the
additional echo suppression may cause incoming audio to occasionally fade in and
out.
NBX Handset
Acoustic Echo
Suppression
Enables additional echo suppression on calls between internal
extensions. Acoustic echo typically occurs when the phone
volume is set to maximum and audio feeds back from the ear
piece to the mouthpiece.
Analog Line Cards
Echo Suppression
Enables echo suppression on calls between internal extensions
and outside callers.
Digital Line Cards
Echo Suppression
Enables echo suppression on calls that use digital line
connections.
Table 36 System Settings Audio Settings Dialog Box Fields (continued)
Field
Purpose