VoiceRD is carefully designed around the Asterisk source code for maximum flexibility. Specific APIs are defi
ned around the central PBX core system. This advanced core handles the internal interconnection of the PBX, c
leanly abstracted from the specific protocols, codecs, and hardware interfaces from the telephony application
s. This allows VoiceRD to use any suitable hardware and technology available now or in the future to perform
its essential functions, connecting hardware and applications.

VoiceRD offers both classical PBX functionality and advanced features, and interoperates with traditional sta
ndards-based telephony systems and Voice over IP systems. VoiceRD offers the features one would expect of a l
arge proprietary PBX system such as Voicemail, Conference Bridging, Call Queuing, and Call Detail Records.

http://www.voicerd.com/VoiceRD_products_voiceRD_opensource.php