Add languages to Asterisk

You may want to add additional languages to Asterisk. You might want to install those in '/usr/local/share/asterisk/sounds/'. If the new sound file directory is called 'Foo' and the language is British English, this becomes '/usr/local/share/asterisk/sounds/en_GB_Foo/'.

Suppose you want to set en_GB as the default English instead of en_US. On a Debian system this means manipulating '/etc/alternatives/';
'/usr/share/asterisk/sounds/en' is a symlink to '/etc/alternatives/asterisk-prompt-en'. And '/etc/alternatives/asterisk-prompt-en' default points to '/usr/share/asterisk/sounds/en_US_f_Allison';

 /usr/share/asterisk/sounds/en -> /etc/alternatives/asterisk-prompt-en
 /etc/alternatives/asterisk-prompt-en -> /usr/share/asterisk/sounds/en_US_f_Allison

First we need to change '/var/lib/dpkg/alternatives/asterisk-prompt-en'.
The default contents is;

auto
/usr/share/asterisk/sounds/en_US

/usr/share/asterisk/sounds/en_US_f_Allison
50

The following adds 'en_GB_Foo' as a possible choice;

~# update-alternatives --install /usr/share/asterisk/sounds/en asterisk-prompt-en /usr/local/share/asterisk/sounds/en_GB_Foo 20

'/var/lib/dpkg/alternatives/asterisk-prompt-en' now contains;

manual
/usr/share/asterisk/sounds/en

/usr/local/share/asterisk/sounds/en_GB_Foo
20
/usr/share/asterisk/sounds/en_US_f_Allison
50

You can now select a new default version of English;

~# update-alternatives --config asterisk-prompt-en

There are 2 choices for the alternative asterisk-prompt-en (providing /usr/share/asterisk/sounds/en).

  Selection    Path                                               Priority   Status
------------------------------------------------------------
* 0            /usr/share/asterisk/sounds/en_US_f_Allison          50        auto mode
  1            /usr/local/share/asterisk/sounds/en_GB_Foo          20        manual mode
  2            /usr/share/asterisk/sounds/en_US_f_Allison          50        manual mode

Press <enter> to keep the current choice[*], or type selection number:

After selecting '1', the symlink now becomes;

 /etc/alternatives/asterisk-prompt-en -> /usr/local/share/asterisk/sounds/en_GB_Foo

Making the sounds used by Asterisk British- instead of American English.
You can download additional sounds from the Asterisk website.