Faxing is only supported on a T1 or analog line, otherwise incoming fax detection and fax quality will be compromised. If you choose to handle faxes over a SIP Provider, then we recommend using T.38.
In Switchvox 5.11.1 and earlier, only one concurrent fax is supported. You must purchase additional fax licenses if you need to send or receive multiple faxes at the same time.
In Switchvox 6.x or later, three concurrent faxes are supported.
Supported Faxing Methods
Sending a fax over the PSTN from the desktop, using a T1 or analog line
Using Switchvox, a user prints a PDF from his or her desktop program, then sends the fax from the Switchvox web suite.
Receiving a fax over the PSTN to the Desktop, using a T1 or analog line
Switchvox can detect fax calls, so a user can have one number (DID) for normal calls and faxes. Faxes are stored as PDFs, and accessed in the web suite or via email notifications.
Sending a fax over the PSTN from an analog fax machine, with an FXS module for the fax machine, and a T1 line
The fax machine can be used normally.
Unsupported Faxing Methods
Receiving a fax on an analog fax machine
Digium does not support this method. With that disclaimer in mind, Digium has seen a good success rate for customers receiving faxes over the PSTN to an analog fax machine plugged into a Digium FXS Card. This method requires you to disable fax detection on the entire channel group which affects your ability to use one number (DID) to receive normal calls and faxes.
SIP Provider using T.38
Digium does not support this method. With that disclaimer in mind, some VoIP Providers and equipment vendors may be compatible with Switchvox’s T.38 implementation. Interoperability testing should be performed to make sure that faxing using your provider or vendor will work with Switchvox.
SIP Provider that is a Digium Gateway using T.38
Digium does not support this method. With that disclaimer in mind, Digium has seen a good success rate for customers sending and receiving faxes this way when Switchvox and the Gateway are located on the same network.
Receiving Fax to a VoIP ATA to an Analog Fax Machine
Sending a fax using G.711 over VoIP
Digium does not support these methods. They may work, but are not supported.
