3Com VCX V7111 VoIP SIP Gateways User Manual 155Supporting V.34 FaxesV.34 faxes do not comply with the T.38 relay standard. 3Com therefore provides the optionalmodes described in “Using Bypass Mechanism for V.34 Fax Transmission “ and “UsingRelay Mode for Both T.30 and V.34 Faxes”.Note that the CNG detector is disabled (CNGDetectorMode=0) in all the following examples.Using Bypass Mechanism for V.34 Fax TransmissionIn this proprietary scenario, the Gateway uses a high bit-rate coder to transmit V.34 faxes,enabling the full utilization of its speed.Use the following configurations as a guide:FaxTransportMode = 2 (Bypass)V34ModemTransportType = 2 (Modem bypass)V32ModemTransportType = 2V23ModemTransportType = 2V22ModemTransportType = 2V21ModemTransportType = 2In this configuration, both T.30 and V.34 faxes work in Bypass mode.OrFaxTransportMode = 1 (Relay)V34ModemTransportType = 2 (Modem bypass)V32ModemTransportType = 2V23ModemTransportType = 2V22ModemTransportType = 2V21ModemTransportType = 2In this configuration, T.30 fax uses T.38 Relay mode while V.34 fax uses Bypass mode.Using Relay Mode for Both T.30 and V.34 FaxesIn this scenario, V.34 fax machines are compelled to use their backward compatibility withT.30 faxes; as a T.30 machine, the V.34 fax can use T.38 Relay mode.Use the following configuration as a guide:FaxTransportMode = 1 (Relay)V34ModemTransportType = 0 (Transparent)V32ModemTransportType = 0V23ModemTransportType = 0V22ModemTransportType = 0V21ModemTransportType = 0Both T.30 and V.34 faxes use T.38 Relay mode. This configuration forces the V.34 faxmachine to operate in the slower T.30 mode.
