In this appendix, we are going to talk about some of the technologies of the traditional telephone network—especially those that people most commonly want to connect to Asterisk. (We’ll discuss Voice over IP in Appendix B, Protocols for VoIP.)

While tomes could be written about the technologies in use in telecom networks, the material included here was chosen based on our experiences in the community, which helped us to define the specific items that might be most useful. Although this knowledge may not be strictly required in order to configure your Asterisk system, it will be of great benefit when interconnecting to systems (and talking with people) from the world of traditional telecommunications.