FAX messages are still a widespread way of exchanging documents between companies. The PBX supports FAX messaging using the T.38 standard in two ways.
First, it connects devices that are supporting the T.38 standard. If you FAX machine is connected to analog terminal adapter (ATA) that supports T.38 and your PSTN gateway also supports T.38, then the PBX will attempt to pass the signals through. While there is no guarantee that this will work flawlessly, there is a reasonable chance that you will be able to continue printing out paper when someone on the other side wants you to do that.
Second, the PBX mailbox can listen to the FAX tone. When it detects a FAX message, it starts to use the T.38 protocol and converts the incoming FAX into an email that is sent to the owner of the mailbox, just like it has just received a voicemail. Because the PBX may have a mailbox for each user, this may eliminate the step to sort incoming FAX messages and it avoids time when dealing with paper.
Passing FAX messages through
If you have a FAX machine, you will need an ATA to receive the FAX calls and convert it into analog signals that you can plug into the FAX machine. This has the advantage that you can also send FAX messages, which is useful when documents need to be signed.
Most ATA devices have some kind of setup that makes sure that the ATA detects the FAX and then switches to the T.38 mode. Sometimes those devices also have settings to turn echo cancellation off, which is neccessary for proper FAX detection (most devices automatically turn echo cancellation off when a FAX was detected).
You can register those ATA as regular extension with the PBX. For the PBX the call will look like a regular call to an extension.
In the auto attendant, you can use the tone
F similar 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.
Converting FAX into emails
When using the Fax2Email feature you will have to configure you Email Settings on the system.
NOTE: It's best not to use the redirection cell phone feature when using the fax setting.
When your email is up and running assign your email address on the Extension Level. You may select in the mailbox settings ("Mailbox enabled") to play a FAX tone instead of the mailbox greeting, but the system will also be able to detect FAX with a standard annoucement. The FAX tone tells the caller that this is a mailbox that was set up to receive FAX messages.
Sometimes customers have specific phone numbers in extensions that are explicity used for FAX and which should convert the FAX into an email. Typically those numbers end on business cards fas "FAX" number. In this case, you can use the setting "FAX DID numbers" in the extension settings to tell the system that when a call hits the numbers listed there, it will not try to call the registered extensions and instead send the call straight to the mailbox.