The "VoIP-4D Primer" is a free guide available in four major languages. The work is an effort to disseminate the use of telephony over the Internet in developing regions. The 40-page guide targets both technical and non-technical readers. The first part presents the essentials of telephony over the Internet. For those interested in the more technical details, hands-on guidelines and configuration files are included in the second part. The examples provide essential background to build your own low-cost telephony system. This work was carried out with the aid of a grant from the Acacia Initiative of the International Development Research Centre of Canada.
The link address is: http://www.it46.se/voip4d/voip4d.php