Asterisk is a communications framework used to build business telephone systems, VoIP gateways, call centres and other real-time communications applications. It provides the underlying telephony engine, allowing developers and system administrators to control how calls are established, routed and processed.
At its heart is the Asterisk dialplan, which defines the behaviour of incoming and outgoing calls. It can connect office extensions, route callers through menus, distribute calls among agents and integrate with external applications. Asterisk works with SIP phones and service providers, as well as conventional telephone networks through compatible gateways and interface hardware.
The software can operate as a standalone PBX or form part of a larger communications platform. Projects such as FreePBX provide a graphical administration interface for organisations that don’t want to manage every aspect of Asterisk through configuration files.
This is free and open source software.
Key Features
- SIP telephony through the PJSIP stack, with support for registration, authentication and endpoint configuration.
- Flexible dialplan for call routing, conditional processing and integration with external systems.
- Interactive voice response (IVR) menus, voicemail, call forwarding, call transfer and call parking.
- Automatic call distribution and queues for handling incoming calls in contact centres.
- ConfBridge audio conferencing with configurable conference rooms and participant controls.
- Call recording, caller ID handling, music on hold and detailed call records.
- Codec negotiation and transcoding between compatible endpoints and networks.
- Asterisk Gateway Interface (AGI) for invoking external programs during call processing.
- Asterisk Manager Interface (AMI) for monitoring, management and call control.
- Asterisk REST Interface (ARI) with WebSocket events for building custom communications applications.
- Modular architecture supporting additional channel drivers, applications and integration services.
Website: github.com/asterisk/asterisk
Support:
Developer: Sangoma Technologies and Asterisk contributors
License: GNU General Public License v2.0
Asterisk is written in C. Learn C with our recommended free books and free tutorials.
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