From mezzoConsult C.B.:
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 interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.
Asterisk provides Voicemail services with Directory, Call Conferencing, Interactive Voice Response, Call Queuing. It has support for three-way calling, caller ID services, ADSI, SIP and H.323 (as both client and gateway).
Check the features section on the official Asterisk web site (http://www.asterisk.org) for a more complete list.
This version adds some custom modules by mezzoConsult (see http://mezzo.net/asterisk)
- app_ldap - ldap support for dialplan.
- app_notify - CallerID notification.
- app_swift - support for Text-To-Speech Cepstral voices in the dialplan.
- res_bonjour - configurable Bonjour support.