Since the release of version 1.8 in 2010, Asterisk has supported connectivity to two external fax modem solutions. The first is the res_fax_digium module that is provided as a part of Digium’s Fax for Asterisk solution. The second is the res_fax_spandsp module that ties into the open source spandsp solution. Digium has continued to support both modules through the lifetimes of Asterisk 1.8, 10, 11 and 12.
Beginning with Asterisk 13, Digium will no longer make available the res_fax_digium module. Instead, users requiring fax capabilities for Asterisk 13 and forward should use the res_fax_spandsp module. Asterisk’s dial plan functionality for use of either res_fax_digium or res_fax_spandsp is nearly identical, allowing for simple migrations.
Users of prior versions of Asterisk can continue to use the Fax for Asterisk or spandsp solutions. Users of Switchvox are not affected by this announcement.
For most Linux users, spandsp is already available as a system library. Otherwise, downloads and FAQs about spandsp may be found at the website – www.soft-switch.org. Questions about the use of res_fax_spandsp may be directed to the Asterisk Forums or to the Asterisk-Users mailing list.
Faxing in Switchvox 6.x has been revamped and no longer requires separate Fax for Asterisk keys. Users of Switchvox 5.x should still use Fax for Asterisk keys for faxing capability.