CallWeaver 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.

CallWeaver talks to a variety of telephony hardware including BRI, PRI, POTS, Bluetooth headsets and IP telephony clients using SIP and IAX protocols protocols