App rpt/Asterisk
App_rpt/Asterisk is a Radio Over IP (ROIP) application which runs on the Asterisk PBX. App_rpt/Asterisk can be used to connect several repeaters and remote bases together using the Internet. App_rpt's primary use is in amateur radio applications, but it could conceivably be used in a commercial environment as well.
App_rpt is an open source project, and there is a hardware interface to the radio which is also open source.
In app_rpt/Asterisk, repeaters and remote bases are known as nodes. Connections are ad-hoc; in other words, and any node may connect to any other node without using anything else other than a direct UDP (User Datagram Protocol) Internet connection from one node to another.