VoIP
Voice over IP (Internet Protocol) is a method of carrying voice conversations over the Internet. The sound is digitized, broken into packets, and sent using the same process by which your Web browser asks for and receives Web pages a chunk at a time. With sufficient network bandwidth, VoIP calls have quite adequate sound quality, but they can suffer considerably if there is any network lag. Methods for creating virtual circuits with guaranteed bandwidth have been essential to the growth of the market for VoIP.
To users, VoIP calls are much like voice telephone calls, except that they have almost zero cost, there used to be serious quality issues, and you originally connected from one computer (with speakers and microphone) to another using Internet addressing. Skype offers free software for computer-to-computer calls, and charges modest rates for global computer-to-telephone calls, based not on long-distance rates, but on the local rates at the destination.
There are now commercial VoIP services in developed countries that use ordinary-looking telephone equipment plugged into a wall jack, supporting calls to any conventional or VoIP telephone, again at very low rates for long distance. Almost all new corporate phone systems now use VoIP.
VoIP is built into the Laptop, together with wireless mesh networking. Since each school is intended to get a server and an Internet connection, all of the children who get Laptops will be able to call each other, subject to the usual constraints on discovering whom it is you really need to talk to.
UN Secretary-General Kofi Annan's Digital Challenge to Silicon Valley some years ago pointed out that VoIP over wireless communications could provide voice communication in developing countries at a small fraction of the cost of a cell phone system, which in turn is a fraction of the cost of copper and fiber optic land lines. In some countries, copper wire is still routinely stolen: dug up from the ground or pulled down from the poles to sell as scrap.
Unfortunately, there are a number of countries, mainly in Africa, where VoIP remains illegal, although there has been and continues to be considerable progress in prying the technologies and markets loose from the previous monopoly telephone companies.
We need some more information on the technology here, and a lot of detail on the progress of VoIP in the target countries for OLPC.