This package contains additional modules for Asterisk which are, for
one reason or another, not included in the normal base distribution.
Many of these modules are experimental or have a GPL license without a
disclaimer that allow digium to insert them into the official
distribution (double licensed).

This work/effort has been sponsored by http://www.mercuriuspbx.it/

Those addons are only for Asterisk 1.4, since 1.6 already include them.
You need the exact spandsp library version as required for the fax
application otherwise it will not work.