Asterisk PBX

Asterisk is a complete PBX in software. It provides all of the features you would expect from a PBX and more. Asterisk does voice over IP in three protocols and can inter operate with almost all standards-based telephony equipment using relatively inexpensive hardware.

Asterisk provides voice mail services with directory, call conferencing, interactive voice response, and call queuing. It has support for three-way calling, caller ID services, ADSI, SIP, and H.323 (as both client and gateway).