Britain’s traditional telephone network, PSTN (and ISDN), is finally getting switched off in December 2025, with modern internet-based solutions set to replace it.

PSTN Switch Off Image
© IMS Technology Ltd. - © Rafael Cosquiere

What is PSTN?

In 1891 an American undertaker named Almon Brown Strowger, of Kansas City, Missouri, discovered the wife of a rival undertaker operated the local telephone switchboard. With this discovery, he realised that when callers were asking to be connected to an undertaker, she was connecting them to her husband, getting him easy business over Strowger.

In response to this situation, Strowger looked at taking bias out of the equation, and so invented the first automatic telephone exchange. This automatic telephone exchange lead to what was later called the public switched telephone network (PSTN), and gave us the ability to dial a unique telephone number, and be automatically connected. The world is now covered in a vast mesh of underground and overhead wires, undersea cables, and satellites, transferring these telephone signals.

In the late 19th century, copper telephone lines were first installed in the UK, some of which are still in use. These lines, and all those added to them over the decades, have become the backbone of our telecoms infrastructure, through PSTN and ISDN. The technology continues to move forwards, however.

What is the replacement?

Technology has progressed more rapidly than ever before in the last 20 years. Therefore a modern solution with room to evolve is needed. This is why Voice over IP (VoIP) is being used. Just like terrestrial television was finally replaced by digital almost a decade ago, telephony is now doing the same thing. PSTN has been looking less able to handle the demands of modern communications over recent years. VoIP on the other hand seemingly has no ceiling that we know of so far. Since it first started gaining traction on PC in the early 2000s, via software like Skype and Ventrilo, VoIP has become widely available on all types of hardware. VoIP has matured, and offers greater clarity, less cost to run, and easily ties into video calls on compatible devices. The benefits don’t end there, however.

Why replace PSTN?

The change from PSTN to VoIP isn’t just because VoIP is newer. It’s because it is open for much great functionality. For instance, you can take calls on any device, from where you are, from the same phone number. If you are working from home, you can take calls from your office phone line just like normal, without using your office handset. You could even do so through your usual mobile phone. VoIP also allows greater connectivity with customers and colleagues. Linking to applications and systems with video chat, and productivity applications like Teams is simple and effective. Also, with everything in the cloud these systems are available anywhere you have an internet connection, and they are easily backed up. Due to the fact it can be accessed from anywhere, it should be no surprise then that the physical footprint of a VoIP system is smaller too. Less hardware is needed in the office, meaning more space, and less maintenance on site.

Will it work?

If you were worried that we might be leading the charge to our doom, you can rest easy. The UK isn’t the first country to turn off PSTN and switch over to VoIP. The switch to digital is happening everywhere, and it’s not taking its time! Germany, Japan, Australia and Sweden are set to complete their switchovers ahead of the UK, and The Netherlands, Estonia and Slovakia have already completed their migrations.

Furthermore, this has been in the making for a few years now, with BT announcing these plans back in the spring of 2018.

What do I need to do?

The main thing you’ll have to do is replace your existing landline handset. Don’t just buy like-for-like replacements, however! Use the opportunity to analyse your current system, and what could be improved. For instance, you could get handsets that have displays and cameras built-in, to allow for straightforward video calling. Or you may wish to forgo handsets altogether and go for a softphone system instead, where employees simply use headsets and a VoIP application on a computer that is linked to a traditional telephone number. This all comes down to your business requirements, and there is no right or wrong answer.

How can we help?

At IMS Technology, we have garnered a lot of experience with VoIP telephony in recent years, and we will be able to provide an informed consultation with you to help you decide what direction you wish to go with your new system. We can also provide and install handsets or softphone systems for you, and support them going forwards.

If there is anything you are still unsure about, or you are interested in changing your phone system over, please do not hesitate to get in touch. One of our expert advisors will happily give you an in-depth, no-obligation consultation.

Interested in learning more?