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What are TDM PBX, Hybrid PBX, and IP PBX? | Part 4

Welcome the fourth segment of our VoIP series. In this blog, we will explain what TDM PBX, Hybrid PBX, and IP PBX are. Most people have no idea what these acronyms mean, how they relate to choosing a phone system, or why they’re important.

TDM (Time Division Multiplexing) PBX (Private Branch Exchange), Hybrid PBX and IP PBX are the main types of phone systems available today. So what, exactly, are they?


TDM PBX is the most common type of voice infrastructure, as it has been around the longest. This model was designed before contemporary server technology was invented, and therefore consists of proprietary, self-contained systems. This system involves a cabinet with many different boards that can be purchased to perform certain functions (such as, intercom functionality boards or analog extension boards).

TDM PBX boards are incompatible with all systems except those from the same vendor as the overall architecture. This can become expensive and limiting. These systems are outdated, and are mostly used by companies that have not updated their network cabling.

Hybrid PBX

Hybrid PBX was created when VoIP became a popular business tool. These systems allow IP phones to connect to the PBX; it is hybrid because it allows both IP and TDM extensions. In addition to connecting extensions through IP, entire cabinets can be distributed and connected to the main system through IP. Many businesses that used TDM PBX have upgraded to hybrid models.

The advantage of the Hybrid PBX is that it cuts down on the costs of a total migration when a company wants to upgrade to VoIP. It modifies existing infrastructure rather than requiring an entirely new system, and is easier for users familiar with the old TDM PBX system to use.


IP PBX architecture involves gateways that establish links between TDM and IP. The main system for this type of infrastructure is a server (or multiple servers) that operates on top-performing hardware. New applications can be added easily.

IP PBX has many advantages, including reduced maintenance costs, increased scalability, voice and data network integration, greater mobility, and SIP capabilities (for more information about SIP, click here).


Simply understanding your options does not necessarily mean that you know the optimal system for your business needs. Therefore, our next blog will address this issue by helping you decide what type of VoIP buyer you are and what elements of VoIP would benefit your business.

If you’ve missed our VoIP series so far, you can find them here:

Part One: Should My Business Switch to VoIP?

Part Two: How to Avoid Potential Problems with VoIP

Part Three: What are the Different VoIP System Features and Options?

>> Activo offers a full range of VoIP options to meet your company’s needs, and we’ll help you determine what is best for your organization. Contact us today!

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