Relay Mode for T.30 and V.34 Faxes

In this scenario, V.34 fax machines are forced to use their backward compatibility with T.30 faxes and operate in the slower T.30 mode.

To use T.38 mode for V.34 and T.30 faxes:
1. On the Fax/Modem/CID Settings page, do the following:
Set the 'Fax Transport Mode' parameter to T.38 Relay (FaxTransportMode = 1).
Set the 'V.22 Modem Transport Type' parameter to Disable (V22ModemTransportType = 0).
Set the 'V.23 Modem Transport Type' parameter to Disable (V23ModemTransportType = 0).
Set the 'V.32 Modem Transport Type' parameter to Disable (V32ModemTransportType = 0).
Set the 'V.34 Modem Transport Type' parameter to Disable (V34ModemTransportType = 0).
2. Configure the [V34FaxTransportType] parameter to [1] (Relay).
To allow V.34 fax relay over T.38:
Set the 'SIP T.38 Version' parameter to Version 3 (SIPT38Version = 3).
To force V.34 fax machines to use their backward compatibility with T.30 faxes and operate in the slower T.30 mode:
Set the 'SIP T.38 Version' parameter to Version 0 (SIPT38Version = 0).

For SBC calls, the device forwards T.38 Version 3 transparently (as is) to the other leg (i.e., no transcoding).