System information

Incoming Fax Handling
Received faxes are commonly encoded in Tagged Image File Format (TIFF). This
graphics file format, while not as well known as JPEG or GIF, is not as obscure as one
might think. In fact, we suspect your computer (whether you’re running Windows,
Linux, or MacOS) will already have the ability to interpret TIFF files built in. While it
has become popular to offer PDF as a delivery format for received faxes, we’re not sure
this is strictly required, since TIFF is so ubiquitous.
Received faxes will be stored by Asterisk as files. Where those files are stored will de-
pend on several factors, including:
• What software you are using to simulate a fax modem (e.g., IAXmodem, Digium
ReceiveFAX, etc.)
• The location in your filesystem that you have configured for storage of received
faxes
• Any post-receipt processing you have decided to perform on the files
In the dialplan, you will need to build in enough intelligence to name faxes in such a
way that they will be distinct from each other. There are many channel variables and
functions that can be used for this purpose, such as the STRFTIME() function. Asterisk
can easily handle capturing the fax to a file, but you will need to make sense out of what
happens to that file once it is stored on the system.
Fax to TIFF
The Tagged Image File Format is not very well known, but it is actually more common
than you might realize, and since it is natively supported on Windows, MacOS, and
Linux, TIFF files can be viewed on pretty much any computer with the most basic
graphics viewer. A subset of the TIFF file format has for a long time been the de facto
file format used for faxes.
Since Asterisk will receive and store faxes in TIFF format, there is no post-processing
required. Once the incoming fax call has been completed, the resulting TIFF file can
be opened directly from the folder where it was stored (or perhaps emailed to the in-
tended user).
Fax to Email
Once Asterisk has received a fax, the resulting TIFF file needs a way to get to its final
destination: a person.
The key consideration is that unless the information that Asterisk knows about the fax
is sufficiently detailed, it may not be possible to deduce the intended recipient without
having someone actually read the fax (it is common for a fax to have a cover page with
the recipient’s information written on it, which even the most capable text recognition
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