5 minute read |

VoIP Phone Service vs TDM – the Pros and Cons

VoIP phone service background

VoIP phone service has taken the business world by storm, supplanting the older TDM (Time Division Multiplexing) technology with astonishing speed. This is not the first time that a particular technology has replaced something slower or inefficient but the quick adoption by enterprises still comes as a surprise. If your business has not already upgraded to VoIP phone service, you may be wondering if you should make that decision.

The easiest way to choose is to find out the benefits and drawbacks of each system. Then decide which set of pros and cons are acceptable to your business. So let’s take a look at VoIP phone service and TDM across various categories that are important to any organization.

Initial and Recurring Costs

Deploying a PBX and PRI lines for a business is not exactly cheap. Most people assume that upgrading will also be expensive but it is not the case with VoIP phone service. The fundamental difference with VoIP and TDM is the way calls are routed across different networks. With VoIP, your calls will actually become cheaper or even free in some cases! So your monthly bill will reduce significantly.

The initial investment is also not exorbitant for VoIP phone service. You may have to replace your existing PBX with an IP PBX and purchase VoIP compatible phones. Small businesses can opt for hosted VoIP services for which you need nothing more than a headset to make calls. Even if you’re not ready to upgrade to VoIP yet, you can at least try out the service without spending much.

Voice Quality

Voice calls made over the POTS are still the gold standard for voice quality and clarity but VoIP service has almost caught up with it. Most businesses are highly satisfied with the voice quality from VoIP systems. This is even truer, now that many vendors offer HD voice for an even better user experience.


TDM lines are your best option if reliability is of utmost importance to your company. With landlines, you never have to worry about downtime for the most part. VoIP phone service is contingent on power and the availability of Internet. So if you lose either one of them, your phones will also fail. Most organizations solve this problem by hooking up the phones to their power backup systems. Still, TDM lines retain the edge when it comes to reliable voice calling.


This is one area where VoIP phone service excels over TDM. VoIP phone systems offer both flexibility and the ability to scale up or down. You can only purchase PRI lines in multiples of 23. If your business needs only 18 or 25, you don’t have an option to purchase that precise number. Either you have to make do with fewer lines or pay for unused capacity. With VoIP phone service, you can purchase exactly the number of lines that you need. The same goes for phone numbers, SIP trunks and any other resource. This flexibility is one of the biggest advantages of VoIP service and the reason why many organizations prefer it over traditional landlines.

Emergency Calling

This was one of the biggest reasons holding organizations back from adopting VoIP phone service but it is no longer an advantage for PRI lines. Many VoIP providers offer E911 which is the digital equivalent of traditional emergency calling. With E911, users can set a location for a particular phone number which will be automatically sent to emergency services if a user calls them from that number. Since VoIP providers are now required by regulators to offer this service, it won’t be long before every VoIP system comes with emergency calling.

Multi-use Versus Dedicated Networks

TDM lines are dedicated solely to voice calling. If you have lines that are not utilized for voice calls, you cannot user for anything else. Since VoIP calling only requires bandwidth, you can utilize any extra capacity for other purposes. Voice calls use the same network as other forms of data so there is no need to have a separate, dedicated network just for making phone calls. This also means you don’t need to worry about maintenance costs of physical wiring.

Moves and Changes

Suppose your office changes its location to a new building. You can’t just take your phones with you. You need wiring in the new space and often this implies waiting for technicians to show up and install everything. With VoIP phone service your phone numbers are connected to you, not a physical location. Your phone number goes wherever you go.

As you can see traditional phones still set the standards for quality and reliability but those attributes are no longer the biggest considerations for enterprises. VoIP phones give you so many more features without sacrificing much in other areas. So it may be time for you to switch too!

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Thousands of businesses across the world trust VoIPstudio for all of their most vital business communications. Why not be the next?

Thousands of businesses across the world trust VoIPstudio for all of their most vital business communications. Why not be the next?

Start a free 30 day trial now, no credit card details are needed!