ISDN/PSTN vs. VoIP. Which is better?

The telephone system you use is old tech. It’s official. 

At least it is if you use an ISDN or PSTN connection for your telephone calls 

Not sure what those acronyms mean? Don’t worry. We’ll explain below. 

The reason why these forms of telecommunication (which have been around pretty much forever) are now coming to the end of their life is because soon we won’t be able to use them. 

In December 2025, BT is switching off the old telephone lines, meaning PSTN and ISDN will be obsolete. If you want to know more about the big switch off and why it’s happening, we’ve got a post on it here.

Fortunately, VoIP technology offers an alternative form of telephony with multiple benefits. Many businesses are already beginning to adopt it. 

A lot of businesses still use a PSTN or ISDN telephone connection. Here’s why you should think about switching.  


What is PSTN and ISDN? 

PSTN and ISDN are the way we have traditionally done telephone communication at home and at work for decades.  

PSTN or Public Switched Telephone Network is just like the basic phone line that you might have at home. While a call is being made that line cannot be used for any other purpose.  

The phone signal is transmitted by good old copper wires installed all over the country 

If you’re a small business, operating a phone primarily for bookings or are a sole trader, this form of simple telephony is perfectly adequate. 

ISDN or Integrated Services Digital Network uses PSTN to operate but digitises the traditional network to provide multiple lines for the business, higher call quality, video and a number of other features.  

Businesses who require multiple numbers, groups, queueing and hold music will go for this option. It still uses a physical PBX (Private Branch Exchange) on the premises but is more flexible than a single PSTN line.  

ISDN is often sold by communication providers who wrap up line rental, broadband and call package deals into the cost. It’s usually not that cheap. 


So, what’s wrong with this technology? 

Nothing’s wrong with these forms of communication as such but they are costly, inefficient and unable to adapt to our changing world. 

Maintenance of the copper wires that these lines rely on comes at great expense and having one phone line to one location with one number is becoming an increasingly old fashioned form of communication.  

At times when a large part of the workforce is working remotely, it isn’t very helpful to have one centralised phone system that can only be accessed from the office or other business premises.  

Most of us need something even more flexible than ISDN. 


VoIP to the rescue 

The undeniable solution for every business is to switch to VoIP and once the switch off happens it will be an essential move. 

VoIP stands for Voice over Internet Protocol. This moves your entire telephony system into the cloud. Calls are taken over the internet and multiple other benefits are provided. 

Instead of a physical PBX on the premises, this is stored in the cloud and call switching is managed from here.  

This is just another example of businesses moving away from old tech and into the cloud 


Reduced cost, plug and play and more 

VoIP has numerous enviable benefits.  

Moving the system to the cloud theoretically provides unlimited scalability and customisation, therefore delivering a solution to suit businesses of any size. 

One benefit that is particularly relevant in today’s world is the ease of use for a remote workforce. The system can be accessed from any device – mobile, tablet and desktop anywhere in the world, whilst still using company numbers.  

In fact, if an entire business were to move premises, they wouldn’t even have to change numbers. They could maintain their current system and avoid the need for any further hardware being installed 

The fact that physical lines don’t need to be installed reduces the cost but it also means the system is plug in and play. You can start using it almost immediately when you sign up to a VoIP provider.  

Communication is completely streamlined. VoIP works alongside your other cloud systems and can include unified comms applications. This means you can collaborate with your teams on projects without having to pick up the phone or arrange a boardroom meeting 

With VoIP calls can be recorded and received over email and you can even get analytics and other useful information that can actually help the business move forward.  


We almost forgot the biggest benefit of them all: It’s cheaper. 

1.5p a minute to be exact. 

Because there are no line rentals and no indirect cost to the consumer from maintenance, the whole thing has a massively reduced cost. 

There’s nothing to install or maintain on your end either. It’s all online, so although there will be some setup fees attached it is minimal compared to what you’d have to pay if you were getting traditional hardware installed.  

Calls are cheaper and VoIP packages are generally charged per person. It’s therefore completely scalable to your business. The fee, which is charged on a monthly basis, will change dependant on how many people are using the system. 


Ok, sounds great, but why worry about this now? 

Hopefully you like the sound of VoIP but you’re probably thinking, that’s great but why do I need to worry about switching now?’ The switchover isn’t happening for another 5 years after all 

Whilst that is true, we still think it’s an important consideration to make. The date in December 2025 will soon catch up on us, especially when the day to day priorities of running a business take over.  

When it happens, it happens for good and you certainly don’t want to be scrambling to make sure your systems are up to date for when it all goes off.  

But besides that, why wait? 

The benefits are clear. It’s cheaper, easier to set up and has many other benefits that improve the flexibility of your business.  

The businesses and organisations who are adopting this tech are ahead of the game and the time and money savings they are able to make will hold them in good stead for the future. 


Let us help 

Of course, changing up your entire telephony system can be daunting but you don’t have to struggle through on your own. 

We have the tools and know-how to make sure you are up and running in no time. If you’re interested in making the switch to VoIP, let us know. 

Getting in touch with us is easy, fill in the form below and a member of our team will be in touch.