FAX
The Vodia PBX supports sending and receiving FAX in two ways: pass-through mode and as FAX endpoint.
Detecting FAX
In the auto attendant, you can use the tone Fsimilar to DTMF tones to send FAX calls to a specific extension. This makes it possible to handle all calls, including calls to a FAX extension, through the auto attendant without manual interaction.
Passing FAX messages through
In FAX pass-through mode, the PBX connects two call legs. Those two legs are regular calls; however often they negotiate a different codec (T.38) to transmit FAX data more reliably.
In the most simple case, there is no T.38 negotiation and the audio stream is just using regular audio packets. This method works well if there is low packet loss and avoids interoperbility problems with negotiating a T.38 connection.
If one of the connected endpoints decides to renegotiate the audio connection and proposes the switch to T.38, the PBX will pass the request through. If the other side accepts the request, the connection will continue on T.38.
Typically the PBX will route the call to an analog terminal adapter (ATA). However any device or service that can receive a FAX can be connected to receive the call.
The FAX passtrough mode expects that the receiving device is connected to the PBX (typically through a registration). Because the call is a regular call for the PBX, the mechanisms to reroute, for example when the registration is lost, the call may send the call to a mailbox. There, the call may be triggering the PBX to act as endpoint.
Receiving FAX on the PBX
When a call hits a mailbox that has the FAX enabled (which is the default), the PBX will start listening for FAX tones. If a FAX message was detected, the PBX will start receiving a FAX.
If the mailbox enabled setting for the extension is set to "FAX", the system will wait only for FAX messages and not record voice messages.
Typically, the mailbox will send a FAX by email. This requires that the email settings have been set up for the PBX and that the extension has an email address. In order to avoid an overflow of the mailbox, the automatic deletion of messages should be set up, e.g. to make room for new messages or after sending a message should be set to delete the message.
In addition to delivering FAX by email, FAX messages can also be viewed and downloaded from the user front end. Especially when mixing FAX and regular voicemail, this can be useful for a regular extension.
The FAX DID numbers list numbers for the user that are considered FAX numbers. When someone calls one of the number, the call is routed to the mailbox and the FXA receiving procedure starts. This makes it possible to have a VoIP phone registered to the extension and receive FAX messages into the same extension.
When a user receives a FAX call on a VoIP phone, a blind transfer into the mailbox using the direct mailbox prefix will start the FAX procedure as well. For example, if the user's extension number is 42, the user should transfer the call to 842.
Sending FAX from the PBX
Users can send FAX from the user front end. If there is a ANI for FAX, the system will prefer this number (subject to the trunk ANI rule) to start the call. The FAX header text will be inserted into the FAX header, which is available on extension and tenant level. If there is no header text, the name for the tenant will be used.