3Com NBX 100 Administrator's Manual page 258

258 C 5: S
HAPTER YSTEM
C
ONFIGURATION
Table 34 lists the codecs supported by the NBX system and describes the
characteristics of each one.
.
Table 34 Supported Codecs
Codec
G.711
No Compression
ADPCM
Medium
Compression
G.729
High Compression
Codecs and NBX Devices
Codecs reside on the NBX devices — telephones, analog terminal
adapters, and so forth. Some older devices do not support the latest
codecs so during call setup NBX devices negotiate an encoding scheme
that is supported by both devices (or all devices on a conference call).
Table 35 lists each device that must encode or decode audio and shows
how each device supports the available codecs.
Table 35 Audio Encoding Supported by NBX Devices
Device
3Com 1102, 2102, and
2102-IR Business
Telephones
3Com 2101 Basic
Telephones
Description
An International Telecommunications Union (ITU) standard for
audio encoding. Encoding and decoding is fast and support is
widespread. Also called MULAW or µLAW. There is a slight
variation called A-law used in European telephone systems.
G.711 provides high quality audio at 64 kbit/sec. G.711
encoding is used by telephone companies worldwide to provide
"toll-quality audio."
Adaptive Differential Pulse Code Modulation (ADPCM) provides
good quality audio at a lower bitrate (32kbit/sec.) than G.711.
The NBX system uses the International Multimedia Association
(IMA) version of ADPCM.
G.729, an ITU standard, employs a more sophisticated
compression technique than ADPCM and it is supported
worldwide. The G.729A codec compresses the audio
information to 8kbit/sec., although processing overhead results
in actual bandwidths greater than 8kbit/sec.
Part Number
3C10121 3C10122
3C10226A
3C10228IRA
3C10226PE
3C10226B
3C10228IRPE
3C10228IRB
3C10281PE
3C10281B
3C10248PE
3C10248B
G.729 ADPCM G.711
No Yes Yes
Yes Yes Yes
Yes Yes Yes