Asterisk: The Definitive Guide 5th by Jim Van Meggelen

Design a complete Voice over IP (VoIP) or traditional PBX system with Asterisk, even if you have only basic telecommunications knowledge. This bestselling guide makes it easy with a detailed roadmap that shows you how to install and configure this open source software, whether you’re upgrading your existing phone system or starting from scratch.
Ideal for Linux administrators, developers, and power users, this updated fifth edition shows you how to set up VoIP-based private telephone switching systems within the enterprise. You’ll get up to speed on the features in Asterisk 16, the latest long-term support release from Digium. This book also includes new chapters on WebRTC and the Asterisk Real-time Interface (ARI).
• Discover how WebRTC provides a new direction for Asterisk
• Gain the knowledge to build a simple but complete phone system
• Build an interactive dialplan, using best practices for Asterisk’s advanced features
• Learn how ARI has emerged as the API of choice for interfacing web development languages with Asterisk