Digium Fax For Asterisk (FFA) was developed out of a strong desire from the Asterisk community to have a Digium-supported fax mechanism in Asterisk. Free for single-channel use, this product can also be licensed from Digium to handle more than one simultaneous fax channel.
Digium FFA can be obtained from the Digium
website (http://www.digium.com). The process of
downloading, installing, and registering this library is thoroughly
documented in the Fax For Asterisk Administrator
Manual, which you can also download from Digium. You will
need to register at the Digium website in order to obtain your free
single-channel fax license key and download the admin manual. There is
also a comprehensive README file included with the
software, which details the steps necessary to get Digium FFA going on
your system.