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Project Description
It explains step-by-step how to build a fully-functional IP PBX using C# in Visual Studio with the help of the prewritten VoIP components of Ozeki VoIP SIP SDK.


A VoIP PBX (Voice over Internet Protocol Private Branch eXchange) is a software-based system that connects telephone extensions of a company to outside public telephone network as well as to mobile networks. A VoIP (or IP) PBX works with VoIP technology allowing audio/video calling and instant messaging communication through the TCP/IP protocol stack for its internal network and interconnects its internal network with the PSTN (Public Switched Telephone Network) for telephony communication.

Figure 1 - VoIP PBX system architecture (Source:

Ozeki VoIP SIP SDK ( provides a first-rate technology for PBX development. Instead of wasting time for long development process on your own, you can take advantage on this decent software development kit. You will see how easy it is to create a PBX when you use Ozeki VoIP SIP SDK. Using this SDK does not require professional programming skills. A basic programming knowledge is enough, since Ozeki VoIP SIP SDK provides the base for the VoIP solution you are working on. Integrating it to your own program will provide instant VoIP ability.

Useful links:

  1. About VoIP technology:
  2. About PBX development:

Last edited Mar 10, 2014 at 10:50 AM by simonrobert, version 3