In 2025 the traditional fixed phone lines that have powered the majority of the UK’s telecommunication network for the past five-plus decades will be turned off permanently.

In what has become known as The Big PSTN Switch-Off, the Public Switched Telephone Network (PSTN) and the additional Integrated Services Digital Network (ISDN), which added more digital capacity to the analogue PSTN lines in the mid 80s, will officially cease in December 2025 when they’re decommissioned by BT Openreach.

But why is this happening now?

And what does it mean for the millions of businesses still using this phone network?

That’s what we look at in this blog.

What is PSTN?

The Public Switch Telephone Network (PSTN) is the traditional copper wire telephone network established in the 19th century to allow phones to call other devices without being privately connected.

Before PSTN, phones had to be connected in pairs for private use between two premises.

ISDN was added later in the mid-80s and added some digital capacity to the analogue PSTN lines.

How does PSTN work?

PSTN uses copper wires to connect phones in homes and commercial buildings, enabling voice calling between devices.

With the introduction of ISDN onto the PSTN lines, the network does have some digital capacity, allowing features like caller ID, call waiting and voice messaging to be completed over the line.

But as communication has become more digital, and with increasing amounts of data needing to be sent over phone lines, PSTN has declined – particularly with the emergence of internet-based communication.

Why is PSTN being turned off?

Simply, the PSTN and ISDN lines don’t have the bandwidth to manage the huge amounts of data passed over them as communication becomes increasingly digital.

With broadband speeds getting ever quicker, communication is now online, and with cloud-based platforms making connections easier and cheaper, PSTN lines have become obsolete.

As a result, BT Openreach announced in 2015 that it would stop investing in the outdated, copper wire-reliant technology.

Another reason PSTN has become outdated because it carries a significant cost and time investment to scale and grow, unlike its VoIP phone system equivalent.

Each new phone requires an individual installation fee for a new line (which can cost several hundred pounds) alongside the investment in the hardware.

These installations can also take a long time because you have to book an engineer visit to come and install the line, and there’s never a guarantee you’ll be able to get an appointment quickly.

 With VoIP, on the other hand, you simply add a new user to your subscription, and they can start work immediately.

Once they’re on the system, they can answer your business’ calls from any internet-enabled device, from anywhere.

When is PSTN being switched off?

BT Openreach announced the end of PSTN and ISDN in 2015, and the process of shutting down the network has been underway since 2020.

The next significant date will be 2023, when BT will stop taking new orders on PSDN lines (so you won’t be able to have any new lines installed).

Finally, by the end of December 2025, the PSTN lines will be switched off entirely. 

Businesses still using PSTN will lose their communication network unless they move over to an internet based system like VoIP (or unless they’ve already moved over before this final deadline).

What happens when PSTN is switched off?

The PSTN switch-off will also include the end of ISDN networks (as this simply adds digital capability to traditional phone lines).

And it’s not just your phone network that will be affected.

Because many more company systems are run using the PSTN and ISDN lines.

By the end of 2025, systems, including door entry systems, CCTV networks, fax machines, PSTN alarm systems and even electronic point-of-sale (EPOS) machines will no longer work if they’re reliant on PSTN and ISDN lines.

So it’s critical you start thinking about how you’ll adapt to keep these systems operational.

Manufacturers are already working on ways for these products to retain the same functionality post PSTN switch-off.

What is PSTN being replaced with?

When PSTN is turned off, communication will become internet based and primarily use cloud-based platforms.

Voice over Internet Protocol (VoIP) is the primary technology that will replace PSTN and ISDN, moving a company’s entire voice, text and video communication onto the internet using a single platform.

These systems can either be hosted using public wifi or on a private server – which best will depend on a business’ individual needs.

What can your business do to prepare for the PSTN switch off now?

Nearly 2.5million SMEs still use PSTN and ISDN in the UK, so there’ll be a lot of preparation that will happen as the 2025 deadline s closer.

The easiest way to prepare for the PSTN switch off is to switch to a VoIP-based phone network.

VoIP puts all your essential business communications online and into one platform so you can more easily manage your calls.

It can also significantly reduce the costs of your phone network because VoIP works on a subscription model from a provider, with prices usually based on a per-user basis.

VoIP allows users to access their business phone numbers on any device with an internet connection.

This makes it perfect for today’s remote and hybrid working world, as employees can work from anywhere and still have access to their numbers.

It’s also beneficial for your customers because they can retain just one business number to call.

Prepare for the 2025 PSTN switch off with Communications Plus

You might be reading this thinking 2025 is a long way away, and you’ve still got plenty of time before you need to start thinking about VoIP or another replacement phone network.

But there are plenty of benefits to switching now.

One is that you can get ahead of the crowd and prepare your business.

While switching to VoIP is easy, it does take time to research the right provider, find the right deal and decide which VoIP hardware is best for you (if you even need the hardware at all).

By switching now, you’ll be able to take your time and find the exact system that matches your specification rather than scrambling with everyone else in a few years.

Also, it takes time to adapt to new technology, and while VoIP is easy to use, there’ll be a bedding-in period once it’s deployed, just as there is with any new technology you introduce.

Getting this period done now means you’ll have an established network up and running when your competition tries to figure everything out.

This allows you to provide a better service and grow your business while they still trying to figure out how VoIP technology works.

At Communications Plus we support businesses to make the upgrade to a cloud based hosted solution seamless and easy.

We’ll migrate any of your existing telephone numbers from your current PSTN/ISDN platform and will help you choose the best hardware and software solution to save your business time and money.

You can also benefit from our bespoke training that ensures you and your team have the knowledge to make VoIP work for you and maximise your return on investment.If you want to find out more about the PSTN switch off or how to move to a VoIP Telephone system, please get in touch