Asterisk has a number of optional build dependencies.  If you intend to
use any analogue PSTN hardware such as DigiumTDM400P, you should install
the dahdi-linux and dahdi-tools software and drivers before compiling
Asterisk.  If you will instead use digital telephony hardware (not IP
phones) such as T1/E1 lines or a PRI, you'll need to install libpri,
again before compiling Asterisk.

Be sure to see /usr/doc/asterisk-1.8.7.2/sample_confs/ after installation
for any additional configuration files you may need.

With 1.8+ release of Asterisk, Add-ons are shipped in the main package.
but disabled by default. Since some of the add-ons are quite useful, this
script will build them, unless ofcourse, the ADDON variable is set as:
ADDONS=no ./asterisk.SlackBuild
The list of pre-selected add-ons is as follows:
app_mysql cdr_mysql chan_ooh323 res_config_mysql