Asterisk is an Open Source PBX and telephony toolkit. It is, in a
sense, middleware between Internet and telephony channels on the bottom,
and Internet and telephony applications at the top. However, Asterisk supports
more telephony interfaces than just Internet telephony. Asterisk also has a
vast amount of support for traditional PSTN telephony, as well. For more
information on the project itself, please visit the Asterisk home page at:

           http://www.asterisk.org

  The official Asterisk wiki can be found at:

           https://wiki.asterisk.org

  In addition you'll find lots of information compiled by the Asterisk
community on this Wiki:

           http://www.voip-info.org/wiki-Asterisk

  There is a book on Asterisk published by O'Reilly under the Creative Commons
License. It is available in book stores as well as in a downloadable version on
the http://www.asteriskdocs.org web site.