Page 97 - Asterisk™: The Future of Telephony

CHAPTER 4

Initial Configuration of Asterisk

I don’t always know what I’m talking about,
but I know I’m right.
—Muhammad Ali

Completing all the steps in Chapter 3 should have left you with a working Asterisk
system. If it did not, please take the time to go back and review the steps, consult the
wiki, engage the community, and get your system running.

Unfortunately, we cannot yet make any calls, because we have not yet created any
channels. To get this plane to fly, we’re going to need some runways. While there are
dozens of different channel types, and dozens of different ways to configure each type
of channel, we just want to get some calls happening, so let’s try and keep things simple.
We have decided to guide you through the configuration of four channels: a Foreign
eXchange Office (FXO) channel, a Foreign eXchange Station (FXS) channel, a Session
*
Initiation Protocol (SIP) channel, and an Inter-Asterisk eXchange (IAX) channel. We
selected these channel types because they are far and away the most popular channel
types in use in small Asterisk systems, and one of the goals of this book is to keep things
as simple as is reasonable. If we cover the basics of these channels, we will not have
done an exhaustive survey of all channel types or topologies, but we will have created
a base platform on which to develop your telecommunications system. Further sce-
narios and channel configuration details can be found in Appendix D.
Our first effort will be to explore the basic configuration of analog interfaces such as
FXS and FXO ports with the use of a Digium TDM11B (which is an analog card with
one FXS port and one FXO port). †

* Officially, the current version is IAX2, but since all support for IAX1 was dropped many years ago, whether
you say “IAX” or “IAX2,” you are talking about the same version.
† This configuration used to be known as the Digium Dev-lite kit. For more information on FXS versus FXO,
keep reading. Put simply, this card will give us one port to connect to a traditional analog line from the phone
company (FXO), and one port to connect to an analog telephone (FXS), which is any type of phone that will
work with a traditional home telephone circuit.

69