The purpose of this chapter is to guide the user 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 protocol (IAX) channel. The purpose is not to give an exhaustive survey of all channel types or topologies, but rather to provide a base platform on which to build your telecommunications system. Further scenarios and channel configuration details can be found in Appendix D. We start by exploring the basic configuration of analog interfaces such as FXS and FXO ports with the use of a Digium Dev-Lite kit. We'll then configure two Voice over Internet Protocol (VoIP) interfaces: a local SIP channel connected to a soft phone, and a connection to Free World Dialup via IAX.
Once you've worked through this chapter, you will have a basic system consisting of many useful interfaces, and you will be ready to learn more about the extensions.conf file (discussed further in Chapter 5), which contains the instructions Asterisk needs to build the dialplan.