At the center of every good universe is a dialplan. The extensions.conf file is the means by which you tell Asterisk how you want calls to be handled. The dialplan contains a list of instructions that, unlike traditional telephony systems, is entirely customizable. The dialplan is so important that rather than defining it in this appendix, we have dedicated all of Chapters 5 and 6, as well as Appendix B, Application Reference, to this topic. Go forth, read, and enjoy!