Asterisk

An open-source software implementation of a telephone private branch exchange (PBX). Asterisk-based telephony solutions offer a rich and flexible feature set. Asterisk offers both classical PBX functionality and advanced features, and interoperates with traditional standards-based telephony systems and Voice over IP systems. Asterisk offers the features one would expect of a large proprietary PBX system such as Voicemail, Conference Bridging, Call Queuing, and Call Detail Records, Call Forwarding, Automated Attendant, Call Parking, Call Recording, Call Routing (DID & ANI), Call Transfer, Call Waiting, Caller ID, Caller ID Blocking, Do Not Disturb, Music On Hold, VoIP Gateways, Voicemail and many more.

Asterisk also supports a wide range of Voice over IP protocols, including SIP and H.323. Asterisk can interoperate with most SIP telephones, acting both as registrar and as a gateway between IP phones and the PSTN. Asterisk developers have also designed a new protocol, IAX, for efficient trunking of calls among Asterisk PBXes.

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