Asterisk PBX

Asterisk is a Private branch exchange system developed using the Open Source methodology. It is designed to operate under the Linux operating system, although ports to FreeBSD and Apple Darwin have been reported. Mark Spencer is the original author.

Many features traditionally available only in high-end PBX systems have been implemented in Asterisk, including voicemail, conference calling, interactive voice response, and automatic call distribution. The system can be extended using a scripting language, and modules may be written in C with a minimum of telephony-specific knowledge. This has led to a significant amount of technological crossover.

Asterisk can interface with a number of PSTN systems, such as T1 lines and ISDN. Additionally, it supports a number of VoIP protocols, including SIP and H.323. The IAX (Inter-Asterisk eXchange) protocol was designed for interfacing multiple Asterisk servers over IP networks.