User guide

Chapter 4—Configuring your VOIP
Multi-Tech Systems, Inc. 29
Field Name
Values
Description
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
To make selections from the Selected Coder drop-down list, the Manual option must
be enabled.
Selected Coder:
“Coder Priority”
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, that
is, 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 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.
AutoCall/Offhook Alert Parameters
Auto Call / Offhook
Alert
AutoCall,
Offhook Alert
The AutoCall option enables the local MultiVOIP to call a remote MultiVOIP without
the user having to dial a Phone Directory Database number. As soon as you access the
local MultiVOIP voice/fax channel, the MultiVOIP immediately connects to the remote
MultiVOIP identified in the Phone Number box of this option.
If the “Pass Through Enable” field is checked in the Interface Parameters screen,
AutoCall must be used.
The Offhook Alert option applies only to FXS channels.
The Offhook Alert option works like this: if a phone goes off hook and yet no number
is dialed within a specific period of time (as set in the Offhook Alert Timer field), then
that phone will automatically dial the Alert phone number for the VOIP channel. (The
Alert phone number must be set in the Voice/Fax Parameters | Phone Number field;
if the VOIP system is working without a gatekeeper unit, there must also be a matching
phone number entry in the Outbound Phonebook.). One use of this feature would be
for emergency use where a user goes off hook but does not dial, possibly indicating a
crisis situation. The Offhook Alert feature uses the Intercept Tone, as listed in the
Regional Parameters screen. This tone will be outputted on the phone that was taken
off hook but that did not dial. The other end of the connection will hear audio from the
“crisis” end as is it would during a normal phone call.
Both functions apply on a channel-by-channel basis. It would not be appropriate for
either of these functions to be applied to a channel that serves in a pool of available
channels for general phone traffic. Either function requires an entry in the Outgoing