Asterisk has a limited ability to pass g729a codec. This features takes a lot of cpu resources and has a low quality. I will explain in this areticle how to expand asterisk support to g729,g723 and g726 with great voice quality and without using critical cpu resources.
in order to utilize HG1600 as a voip transcoder we will use the LCR feature: The diagram is as follows:

VoIP Provider X.X.X.X <--->  HG 192.168.9.2 <---> Asterisk PBX 192.168.9.10

HG Configuration
1. goto Configure->LCR-> Media connections, and assign all LCR channels to MG.0(11) (VoIP Media Gateway)



2. goto Configure -> LCR -> Groups and create two groups, voipin and voipout:


3. Goto Counfigure -> LCR -> Resource Map and assign the first 15 channels to voipin and the second 15 channels to voipout:


4. Goto Manage -> VoIP -> Phone2Net Dial Plan and set all prefixes to go through Asterisk server:

Asterisk Configuration:
sip.conf:

[hmgw]
host=192.168.9.2
disallow=all
allow=alaw
allow=ulaw
type=peer
context=test-cc
insecure=port
canreinvite=yes
nat=no

Asterisk SIP configuration include only alaw and ulaw codecs, this way we leave the transcoding to HG.

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