Altigen ACM 6.7 Administrator's Manual page 233

Setting an IP Extension
When an IP phone registers to an IP extension, the system will check the IP address to
determine which codec to use for the IP phone.
For local IP phone deployment
If your local IP address is not in the pre-configured range, you need to add the local IP
address range into the IP Codec setting. Otherwise the system will use the Default
(Prefer G.723.1 support G.729) setting for your IP extensions.
For remote IP phone deployment
If you do not enter the remote IP phone's IP address into the IP Codec table, the system
will use the Default (Prefer G.723.1 support G.729) setting. You can change the Default
to Prefer G.729 support G.723.1, if desired.
To set up the VoIP codec and define IP address ranges, see "Setting VoIP Codec Profiles"
on page 319 and "Assigning Codec Profiles to IP Addresses" on page 322.
MAXCS ACM 6.7 Administration Manual 219