SIP Trunking and Open Source PBX Systems

SIP and Open Source PBXWe’ve written a lot about how businesses can achieve significant savings by switching to SIP. Those interested in slashing costs even further have another option to explore– free, open source PBX systems. These solutions offer all of the state-of-the-art unified communications features you need, without any cost for the software. All you pay for is the server that runs the solution and any consulting services you need to get it up and running. There are many options available. Here is an introduction to the most popular.

Asterisk by Digium

The Asterisk solution by Digium is one of the most popular PBX solutions in the world. There are more than one million Asterisk-based PBX systems in use in more than 170 countries. Asterisk is a free, open source foundation for building all sorts of communications applications. It is often connected to the public telephone network via SIP trunks. It runs on a regular computer and can be used as a standalone phone system, or it can be used to extend an existing PBX.

We should note that Asterisk was built by developers for developers. In order to customize the solution, one must understand Linux, telephone, script programming and networking. But thousands of businesses without these skills still use Asterisk by leveraging an integrator or consultant. The AsteriskExchange community marketplace, which contains a list of pre-built solutions is also a good option.


FreePBX is an open source graphical user interface that controls and manages Asterisk. It is easy to use and customize and can be run in the cloud or on a site located server. It can work alone, but is often installed as part of a distribution that includes Asterisk, the OS, the user interface and other dependant software. It is a great solution for home-based businesses as well as large, multi-location enterprises.

There are commercial models available and paid support, integration and other services are options. FreePBX works perfectly with most SIP trunking solutions.


FreeSWITCH is a telecommunications solution that uses common protocols to deliver voice, text and other media. It is a platform on which many telephony capabilities can be developed using free tools. It supports several audio codecs, making it a good match for SIP trunking. Development is simplified because of its modular design. The solution is packed with modules to enable basic functions as well as more sophisticated features.

These are just some of the open source telephony solutions available. We also recommend checking out Elastix and PBX in a Flash. Before you decide on a solution, make sure that your SIP trunking provider will work with the one you select. (SIP.US works with all of these as well as many more.)

We think that an open source PBX is a great way to go for many businesses, but getting one set up and working with all of the features you need does require some technical know-how, so if you aren’t a telco and networking pro, it is a good idea to invest in a consultant or integrator.

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