User's Manual

Avaya Branch Gateway Manager 10.0 Page 183
15-601011 Issue 29r (Friday, November 02, 2012)B5800 Branch Gateway
Configuration Settings: System
5.3.12 VCM
This form allows adjustment of the operation of any Voice Compression Modules (VCM's) installed in a control unit.
· The options for IP400 VCM controls are supported on IP400 systems from the Release 3.2/4.0 Q2 2007
Maintenance Releases onwards.
· The same controls are supported for IP400 VCM cards in IP500 systems from Release 4.1 Q1 2008
Maintenance Release onwards.
· The options for IP500 VCM controls are supported from Release 4.2 onwards.
Calls to and from IP devices can require conversion to the audio codec format being used by the IP device. For systems
this conversion is done by voice compression channels. These support the common IP audio codecs G.711, G.723 and
G.729a. For details of how to add voice compression resources to a system, refer to the Avaya Branch Gateway
Installation Manual.
When are Voice Compression Channels Used
The voice compression channels are used as follows.
· IP Device to Non-IP Device
These calls require a voice compression channel for the duration of the call. If no channel is available, busy
indication is returned to the caller.
· IP Device to IP Device
· Call progress tones (for example dial tone, secondary dial tone, etc) do not require voice compression
channels with the following exceptions:
· Short code confirmation, ARS camp on and account code entry tones require a voice compression
channel.
· Devices using G.723 require a voice compression channel for all tones except call waiting.
· When a call is connected:
· If the IP devices use the same audio codec no voice compression channel is used.
· If the devices use differing audio codecs, a voice compression channel is required for each.
· Non-IP Device to Non-IP Device
No voice compression channels are required.
· Music on Hold
This is provided from the system's TDM bus and therefore requires a voice compression channel when played to an
IP device.
· Conference Resources and IP Devices
Conferencing resources are managed by the conference chip which is on the system's TDM bus. Therefore, a voice
compression channel is required for each IP device involved in a conference. This includes services that use
conference resources such as call listen, intrusion and silent monitoring.
· Page Calls to IP Device
Page calls require 1 voice compression channel per audio codec being used by any IP devices involved. The system
only uses G.729a for page calls, therefore only requiring one channel but also only supporting pages to G.729a
capable devices.
· Voicemail Services and IP Devices
Calls to the system voicemail servers are treated as data calls from the TDM bus. Therefore calls from an IP device
to voicemail require a voice compression channel.
· Fax Calls
These are voice calls but with a slightly wider frequency range than spoken voice calls. The system only supports
fax across IP between systems with the Fax Transport option selected.
· SIP Calls
· SIP Line Call to/from Non-IP Devices
Voice compression channel required.
· Outgoing SIP Line Call from IP Device
No voice compression channel required.
· Incoming SIP Line Call to IP Device
Voice compression channel reserved until call connected.
· T38 Fax Calls
The system supports T38 fax on SIP trunks and SIP extensions. Each T38 fax call uses a VCM channel.