OpenPBX is an Open Source PBX and telephony development platform that
can both replace a conventional PBX and act as a platform for developing
custom telephony applications for delivering dynamic content over a
telephone similarly to how one can deliver dynamic content through a
web browser using CGI and a web server.
OpenPBX talks to a variety of telephony hardware including BRI, PRI,
POTS, Bluetooth headsets and IP telephony clients using SIP and IAX
protocols protocol (e.g. ekiga or kphone). For more information and a
current list of supported hardware, see www.openpbx.org.