I’ve created an archive of the links used for researching a paper, A Low Density VoIP/PSTN Gateway. The paper describes setting up a “personal PBX” using Asterisk, an open source software program which runs under Linux. With domestic long-distance rates coming down, internet calls themselves may not be as interesting from an economic standpoint. But, using the Asterisk program and an old PC anyone can create an inbound or outbound call center, IVR (interactive Voice Response) system, or branch and headquarters phone system.