I have a customer that shares a PRI with a local FAX server and a PBX, about 40 DID's are dedicated to the FAX server. I am having issues with FAX completion, after many config changes we are going to route the dedicated DID's through a T38 trunk. My question is, in the 904 when I enable Modem pass-through and enable T38 will the codec be used only on FAX tone detection.
voice trunk T02 type isdn
description "PRI to PBX"
resource-selection linear ascending
caller-id-override number-inbound xxxxxxxxxx
connect isdn-group 1
rtp delay-mode adaptive
codec-list "SIP to PRI"
Yes, it will only come into play when a fax is detected. Voice calls will not be affected by T38 settings.