Asterisk is the world’s leading open source telephony engine and tool kit. Offering flexibility unheard of in the world of proprietary communications, Asterisk empowers developers and
integrators to create advanced communication solutions...for free.

Asterisk® is released as open source under the GNU General Public License (GPL), and it is available for download
free of charge. Asterisk® is the most popular open source software
available, with the Asterisk Community being the top influencer in
VoIP.

Asterisk as a switch (PBX)

Asterisk can be configured as the core of an IP or hybrid PBX, switching calls, managing routes, enabling features, and connecting callers with the outside world over IP, analog (POTS), and digital
(T1/E1) connections.

Asterisk runs on a wide variety of operating systems including Linux, Mac OS X, OpenBSD, FreeBSD and Sun Solaris and provides all of the features
you would expect from a PBX including many advanced features that
are often associated with high end (and high cost) proprietary PBXs.
Asterisk's
architecture is designed for maximum flexibility and supports
Voice over IP in many protocols, and can interoperate with almost
all standards-based telephony equipment using relatively inexpensive
hardware.

Asterisk as a gateway

It can also be built out as the heart of a media gateway, bridging the legacy PSTN to the expanding world of IP telephony. Asterisk’s modular architecture allows it to convert between a wide
range of communications protocols and media codecs.

Asterisk as a feature/media server

Need an IVR? Asterisk’s got you covered. How about a conference bridge? Yep. It’s in there. What about an automated attendant? Asterisk does that too. How about a replacement for your aging
legacy voicemail system? Can do. Unified messaging? No problem. Need
a telephony interface for your web site? Ok.

Asterisk in the call center

Asterisk has been adopted by call centers around the world based on its flexibility. Call center and contact center developers have built complete ACD systems based on Asterisk. Asterisk has also
added new life to existing call center solutions by adding remote IP
agent capabilities, advanced skills-based routing, predictive and
bulk dialing, and more.

Asterisk in the network

Internet Telephony Service Providers (ITSPs), competitive local exchange carriers (CLECS) and even first-tier incumbents have discovered the power of open source communications with Asterisk.
Feature servers, hosted services clusters, voicemail systems,
pre-paid calling solutions, all based on Asterisk have helped reduce
costs and enabled flexibility.

Asterisk everywhere

Asterisk has become the basis for thousands of communications solutions. If you need to communicate, Asterisk is your answer.