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Chapter 4: Configuring your VOIP
Multi-Tech Systems, Inc. 37
Voice/Fax Parameter Definitions (continued)
Coder Parameters
Coder Manual or
Automatic
Determines whether selection of coder is manual or automatic.
When Automatic is selected, the local and remote voice channels
will negotiate the voice coder to be used by selecting the highest
bandwidth coder supported by both sides without exceeding the
Max Bandwidth setting. G.723, G.729, or G.711 are negotiated.
Selected Coder
(SS models only)
G.711 a/u law 64 kbps;
G.726, @ 16/24/32/40 kbps;
G.727, @ nine bps rates;
G.723.1 @ 5.3 kbps, 6.3 kbps;
G.729, 8kbps;
Net Coder @
6.4, 7.2, 8, 8.8, 9.6 kbps
Select from a range of coders with specific bandwidths. The
higher the bps rate, the more bandwidth is used. The channel
that you are calling must have the same voice coder selected.
Default = G.723.1 @ 6.3 kbps, as required for H.323. Here 64K
of digital voice is compressed to 6.3K, allowing several
simultaneous conversations over the same bandwidth that would
otherwise carry only one.
To make selections from the Selected Coder drop-down list, the
Manual option must be enabled.
Selected Coder
G.711, G.729
-or-
G.729, G.711
Coder Priority has two options (G.711,G.729 or G.729, G711) on
the Selected Coder listing of the Coder group on the Voice/Fax
screen. If G.711 is the higher priority, i.e., G.711 is preferred to
G729 on the sending side, then G.711, G.729 option is selected.
Similarly, if G.729 has the higher priority, then G.729, G.711
option is selected.
It is used whenever a user wants to advertise both G.711 and
G.729 coders with higher preference to a particular coder.
It is useful when the calls are made from a particular channel on
the VOIP to two different destinations where one supports G.711
and the other supports G.729.
Max bandwidth
(coder)
11 – 128 kbps
This drop-down list enables you to select the maximum
bandwidth allowed for this channel. The Max Bandwidth drop-
down list is enabled only if the Coder is set to Automatic.
If coder is to be selected automatically (“Auto” setting), then enter
a value for maximum bandwidth.
Advanced Features
Silence
Compression
Y/N Determines whether silence compression is enabled (checked)
for this voice channel.
With Silence Compression enabled, the MultiVOIP will not
transmit voice packets when silence is detected, thereby
reducing the amount of network bandwidth that is being used by
the voice channel (default = on).
Echo
Cancellation
Y/N Determines whether echo cancellation is enabled (checked) for
this voice channel.
Echo Cancellation removes echo and improves sound quality
(default = on).
Forward Error
Correction
Y/N Determines whether forward error correction is enabled
(checked) for this voice channel.
Forward Error Correction enables some of the voice packets
that were corrupted or lost to be recovered. FEC adds an
additional 50% overhead to the total network bandwidth
consumed by the voice channel (default = Off).
Table is continued on next page…