Let's work from the inside out. The types of call progress tones
played to the callers once they are within Asterisk are set in
indications.conf, which is, of course, one of the many .conf files
to be found in the /etc/asterisk directory.
"On opening indications.conf, you will find that the default set
of tones to be used (by the pbx_indications module) is specified in
the [general] section with a two letter country code.
"The next example, shows the way the first few lines of the file
look on a fresh installation, prior to any changes:"