How To Prepare for the ISDN and PSTN switch off

Did you know that BT is switching off all ISDN and PSTN phone lines in 2025? Do you know how to prepare for it? If you answered no to either of these questions, fear not as Clarion Communication Management are here to walk you through it. By teaching you more about the ISDN switch-off, VoIP telephone Systems and the telecoms industry, we can make the change easy and less daunting.

By December 2025, the Public Switch Telephone Network (PSTN) and the Integrated Services Digital Network (ISDN) will be switched off permanently by the Telecoms giant, BT. This means that every phone line, be it within a school, home, or business will be forced to make the switch to a fully digital VoIP phone system.

While the move to digital may seem natural to most tech-savvy UK citizens, this switch-off will still make a huge impact on the infrastructures of millions across the country. In fact, this change is so impactful that the National Business Communications has reported nearly 70% of UK businesses are still using landlines within their company, despite the number of consumer landlines declining.
So, if you’re not already familiar with VoIP, how the ISDN switch-off will impact you or how to prepare for it, this is the guide for you.

ISDN switch off / isdn line / voip telephone systems

Why is the ISDN line being switched off?

As the inevitable BT Switch Off looms closer, schools and businesses across the UK must start preparing for a huge technological change. The copper-based PSTN and ISDN network has been largely unaltered since the 1980s and while to many it seems reliable, it is simply out of date. These outdated technologies that have been used by us all for over 30 years are found to no longer be able to deliver the volume of quality voice data needed in an increasingly digital world. At the time of the ISDN line installation, it provided a vastly improved service that allowed users to transmit not only voice data but video and other data as well. However, with many technological advances coming into our lives since the 80s, it is simply no longer up to the task.

The switch-off will inevitably impact both business and home phone telephone lines and even impact other non-voice services connected to PSTN or ISDN lines such as:

  • Security alarms
  • CCTV systems
  • EPOS machines
  • Lift alarms
  • Lines delivering Broadband services

This digital migration does mean that older lines and hardware (as mentioned above) that still rely on this technology will no longer function after the 2025 deadline. But don’t worry, there are many modern and cost-effective alternatives that schools and businesses can turn to. As long as you have a handset that can use internet protocol (IP) technology to transmit voice in a digital format using a broadband connection when you make or receive a phone call, you should be fine. This is otherwise known as VoIP.

VoIP will undoubtedly pave the way for a cheaper alternative to PSTN or ISDN for thousands of users across the UK. VoIP phone systems not only provide a more straightforward solution to analyse and track statistics of usage and other important data but also reduce the costs of these services.

What is VoIP?

Due to enormous financial and infrastructural investment in super-fast fibre broadband across the country, there are a number of alternatives being widely offered to all businesses, schools and homes. Voice over Internet Protocol (VoIP) is an innovative cloud-based phone system which ensures that all calls are sent over your broadband line instead of the outdated copper ISDN Lines.
Upgrading and changing your telecoms systems becomes much simpler with VoIP too. Instead of the long process of setting up physical networks for individual businesses or schools that allow internal calling and re-routing calls, these useful admin features can be easily added, updated or removed without the need for a physical network.
Some other VoIP benefits include:

  • Reliability – The cloud telecoms platform supports thousands of businesses, institutions, and infrastructures across the world. It gives users the ability to take their business phones with them with nothing more than a softphone app.
  • Security – VoIP can mitigate annoying security threats such as phishing by leveraging technology, such as encryption and improved identity management.
  • Cost – Telecoms experts estimate that migrating to a VoIP phone system can save businesses up to 60% in telecommunication costs. With VoIP, businesses can cut ongoing expenses such as call charges, repair, and maintenance fees.

Upgrade to VOIP

    Why Work With Clarion?

    For over 20 years, Clarion has earned the reputation of being a leading provider of VoIP phone systems for schools, colleges, charities and business across the UK. Throughout our impressive history, we have successfully managed the implementation of innovative, cost-effective voice and data services to over 10,000 companies and have a long list of happy customers.

    To get ahead of the ISDN switch off and upgrade your telecoms infrastructure, simply get in touch with the team today or fill out the form above. Our team of hosted VoIP Consultants will happily walk you through all the available options and help you improve the way your business communicates.


    • "Clarion enabled all our staff to be set up quickly and efficiently as remote workers via mobile applications and softphones so that we can continue to work remotely as if we were using the office phone system."

      Adam Southam, Director FRONTrunner Recruitment
    • "In the end we went for the best value and best technology. The choice was obvious because the simplicity, features and cost-effective capabilities of 3CX really stood out"

      Aron V Davies Education Impact Academy Trust
    • "The transition from our old phone system to new has been seamless. It was clear from the very start of the project that Clarion had the knowledge and commitment to ensure the project would be a success, saving us time and money in the process. The support they have provided post project has also been second to none."

      James Sadler Assistant Bursar, Crosfields School
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