In regular telephone systems, a PBX (private branch exchange) is the switching system that manages calls between internal or local users. It also shares a number of lines that connect to the external, public phone system and parcels them out as needed to the local users.

In VoIP or IP telephony systems, the IP PBX does all this and more. It performs all the switching and connecting of VoIP calls. In many cases it does the same for regular telephone calls (in systems that can handle both kinds of phone system). It is also highly programmable and can perform advanced functions including voice menu systems, automatic call conferencing, click-to-call (click on a contact record on a PC screen to initiate a voice call), call logging and tracking and much more. Using an IP PBX system and VoIP telephone service allows an organization to combine (or converge) voice and data networks into a single system for cost-savings, simpler management and greater functionality.

Typically an IP PBX system is a piece of software running on a server . Depending on the workload, that server can also be performing other tasks, but usually it is dedicated and also acts as the VoIP system's connection to the internet. IP-PBX systems can come as software for you to install on an existing server of your own, or as preconfigured software on a server, or even as a turnkey box that is completely set up in advance to just connect to your existing network.

Why you need an IP PBX

Any IP telephony setup that is for more than two or three lines needs a switching system to make it more efficient, allow internal calling and switching between users and to provide more advanced features like voicemail, call forwarding, call hold, conferencing and more. Typically IP PBX systems become economically sensible with as few as 5 users and a good rule of thumb is that if you want an IP telephony system with extensions for your users than you will want an IP PBX.

In addition, market and analyst estimates show that there is a rapid migration to IP telephony underway because of cost, efficiency and performance advantages. Any organization, even a small one that migrates to VoIP or IP telephony will need an IP PBX system. In the past PBX systems for organizations and enterprises cost so much that only large enterprises could afford to make use of them, but recent technological advances and pressure from open source solutions has brought the cost of IP PBX systems down to as low as well under $1000.

What you need in an IP PBX

There are dozens of IP PBX systems and most of them can do an adequate job. Regardless of the size of your organization, any IP PBX should be able to do the following:

• Automated attendant-an automatic system to answer phones with the ability to build phone menu systems, add call menus, transfer to voicemail and create flexible and programmable rules to handle all of these features.
• Call menus-flexible call management menus with user selectable options. More advanced version of the traditional phone tree/menu systems. A better quality system will allow you to have multiple sets of menus and even change them based on time or on information gleaned from caller ID.
• Managing extensions-features to help the phone system administrator by allowing the addition of new extensions, removal of unneeded extensions, change of extension locations and much more from a web-based control panel.
• Voicemail and voice mailboxes-any IP-PBX should allow an almost infinite number with far more flexibility than regular phone systems. More advanced features would include the ability to record ALL incoming and outgoing conversations automatically.
• Call forwarding-automatic, programmed or manual call forwarding to any number.
• Call hold-placing callers properly on hold with no drop off in queues with user selectable hold music and programmable options about handling hold time length.
• Conference calling-handling multi-party conference calls -- internally an externally
• Branch office support-the ability to manage and remotely administer extensions at other offices just as easily as if they were local
• Web-based management and administration-to make it quick and easy to manage your phone system directly from a web browser -- this can include the ability to add end-user configuration and management functions as well.
• Some form of integration into your basic data network so that 'click-to-call' functionality can be added or even full blown CRM systems.

Who makes IP PBX Systems?

Some of the manufacturers and vendors for IP PBX include:

Alcatel, Avaya, Cisco, Dialexia, Digium, Fonality, Mitel, Nortel, Pingtel, Shoretel, Siemens, Nec and Talkswitch.

How do I evaluate VoIP systems and IP-PBX Systems?

The simplest way is to look through the information on the VoIP-News site and the IP-PBX Resource Center in particular. If you are looking to understand more about VoIP for small and medium business VoIP, look at our Buyer's Guide. And if you are know you are more seriously interested or want to explore your IP PBX options, look at our IP-PBX Guide.

Who can I talk to?

If you are ready to take your exploration of VoIP further, we can put you in touch with a VoIP News analyst to help you sort out your options. Alternatively, we can arrange for you to get a set of quotes on a system from a range of reputable VoIP vendors.