Asterisk

"With Asterisk, no one is telling you how your phone system works, or what technology you are limited to.  If you want it, you can have it.  Asterisk lovingly embraces the concept of standards compliance, while also enjoying the freedom to develop it's own innovations.  What you chose to implement is up to you, Asterisk imposes no limits."1

Asterisk is an open source, converged telephony platform which is designed to run on Linux.  A complete Private Branch Exchange (PBX) in software, Asterisk combines over 100 years of telephony knowledge into a robust suite of tightly integrated telecommunications applications.  The power of Asterisk lies in the combination of its customizable nature and unmatched standards-compliance.  No other PBX can be deployed in so many creative ways.

Applications such as voicemail, hosted conferencing, call queing, music on hold, and call parking are all standard features built right into the software.  It has support for three-way calling, caller ID services, SIP and H.323 protocols. More over, Asterisk can integrate with other business technologies in ways that closed, proprietary PBXs can scarcely dream of.  This amounts to an agile and flexible system that is built, by design, to grow and evolve as requirements change. 

What follows is a partial list of features that are built into Asterisk system.  The list grows each day as Asterisk  rewrites the rules of telecommunication.
  • Alarm Receiver
  • Append Message
  • Authentication
  • Automated Attendant
  • Blacklists
  • Blind Transfer
  • Call Detail Records
  • Call Forward on Busy
  • Call Forward on No Answer
  • Call Forward Variable
  • Call Monitoring
  • Call Parking
  • Call Queuing
  • Call Recording
  • Call Retrieval
  • Call Routing (DID %26 ANI)
  • Call Snooping
  • Call Transfer
  • Call Waiting
  • Caller ID
  • Caller ID Blocking
  • Caller ID on Call Waiting
  • Calling Cards
  • Conference Bridging
  • Database Store / Retrieve
  • Database Integration
  • Dial by Name
  • Direct Inward System Access
  • Distinctive Ring
  • Distributed Universal Number Discovery (DUNDi)
  • Do Not Disturb
  • E911
  • ENUM
  • Fax Transmit and Receive (3rd Party OSS Package)
  • Flexible Extension Logic
  • Interactive Directory Listing
  • Interactive Voice Response (IVR)
  • Local and Remote Call
  • Agents
  • Macros
  • Music On Hold
  • Music On Transfer
  • Predictive Dialer
  • Privacy
  • Open Settlement Protocol (OSP)
  • Overhead Paging
  • Protocol Conversion
  • Remote Call Pickup
  • Remote Office Support
  • Roaming Extensions
  • Route by Caller ID
  • SMS Messaging
  • Spell / Say
  • Streaming Media Access
  • Supervised Transfer
  • Talk Detection
  • Text-to-Speech (via Festival)
  • Three-way Calling
1     Asterisk: the Future of Telephony, by Jim Van Meggelen, Jared Smith and Leif Madsen.  Copyright 2005 O'Reilly Media Inc.