User guide

Wireless technologies come in many flavors and their performance depends on the particular
application.It was not until spring 2004 I first heard about a piece of free software that was able to do
exactly what I needed. I was living in Tanzania with an unreliable phone line and prohibitive phone
tariffs. As soon as I managed to get Internet access, I started to call abroad using a well known
proprietary telephony software but I soon felt frustrated because it did not give me the flexibility I
needed. What I really wanted was to use my Internet access in Tanzania to be able to place phone
calls via my own office in Sweden and be able to offer that voice connection to others.
The idea of using the Internet as an alternative to the telephone network was not new, but the software
that made it possible certainly was “revolutionary”. The piece of software that could convert any
computer to a telephone exchange was called “ Asterisk .”
1
It did not take me much time to realise that
that piece of free software was able to do far more that I could ever imagine and opened an
unimaginable world of opportunities for communities in both the developed and developing world. The
feeling was much like my very first connection to the World Wide Web in 1994.
No doubt, the experience of learning how to set up Asterisk was painful and although some very good
books are now available, I have not seen any document that introduces some basic concepts to
common human beings in an intuitive manner. This “primer” is an attempt to introduce you to those
essentials of IP telephony and give you some concrete examples of the potential use in developing
regions. As the goal was to create a short but not necessarily simplistic document, a big part of this
effort has been to be as pedagogical as possible.
Be patient. Your persistence is the key for self-learning.
Before describing how you can build your own telephony system, we introduce the essentials of
telephony over the Internet (Sections 2 and 3). Take the time to read through these sections - in the
long run, understanding the basic concepts is far more important than installing the software.
For those who want to put theory into practice, the two following sections cover how to build a PBX
including assembling the hardware (Section 4) and installing the software (Section 5).
Instead of listing all possible commands and endless configuration options, we have selected three
practical scenarios as basic examples. Remember that the goal is to get you started. The three
scenarios are:
1. Asterisk is an open source project based on ideas of the “Zapata Telephony Project”.
http://www.asteriskdocs.org/modules/tinycontent/index.php?id=10
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