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T.38 FAX Detection

Hello,

I have a problem with the recognition of T.38 faxes; my customer has migrated its telephony provider to T.38 and the fax Onramp does not work.

I think there is a problem in the script recognition, the fax detection. Fax detection script is updated to app_fax_detect.2.1.2.3.tcl.

Configuration is the following:

application

Service fax_detect flash: / / app_fax_detect.2.1.2.3.tcl

dial-peer voice 3 pots

Service fax_detect

incoming called-number 123456789

direct-inward-dial

port 0/0/0: 15

!

dial-peer voice 5 mmoip

service fax_on_vfc_onramp_app out-bound

destination-pattern 9989

information-type fax

session target mailto: users@customer.com

Where is the error?

Thanks to all!

1 REPLY
Silver

Re: T.38 FAX Detection

1. An incoming call is initially established as a voice call.

2. The gateways advertise capabilities in an SDP exchange during connection establishment.

3. If both gateways do not support T.38, fax pass-through is used for fax transmission. If both gateways do support T.38, they attempt to switch to T.38 upon fax tone detection. The existing audio channel is used for T.38 fax relay, and the existing connection port is reused to minimize delay. If failure occurs at some point during the switch to T.38, the call reverts to the original settings that it had as a voice call. If this failure occurs, a fallback to fax pass-through is not supported.

4. Upon completion of the fax image transfer, the connection remains established and reverts to a voice call using the previously designated codec, unless the CA instructs the gateway to do otherwise. If the CA has been configured to control fax relay, the CA instructs the gateway on processing the call with the fx: extension of the local connection option (LCO).

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