Prepare for the PSTN / ISDN switch off in 2025

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PSTN / ISDN switch off – Making the switch to modern business communications and connectivity

The biggest change in decades to the UK’s telephone network is fast approaching, and we’re here to help you get prepared for the future and make sure there’s no disruption to your business.

The Public Switch Telephone Network (PSTN) will be switched off in December 2025 affecting ISDN services too as it makes way for more up-to-date technology. With copper phone lines degrading fast and being replaced by faster, fibre solutions, modern businesses are looking to more flexible, affordable and scalable solutions as a new solution.


Helping to answer your PSTN questions

PSTN and ISDN technology will be switched off in 2025 by Openreach with stop-sell happening in 2023. This means that everyone using PSTN-based services will need to find alternative solutions to make voice calls and connect to fibre solution. If you’re one of the million UK businesses still using it, you need a plan to move.

ISDN was launched in the late 1980’s to make and receive multiple calls into businesses. ISDN splits the traditional copper phone line (PSTN) into multiple digital channels allowing people to make and receive calls simultaneously on the one physical line. With the whole service relying on copper wires, it’s been degrading over the past 30+ years and can’t keep up with the faster connection speeds provided by new fibre technology.

ISDN is now way past its expiry date – just think about your life in the 1980’s compared to today. Are you still wearing a shell suit, creating mixer tapes from the Top 40 countdown and driving a Ford Sierra? No, of course not, you’ve moved on and so should your communications.

If you’re using PSTN or ISDN services, you will be affected. As of 2023 you will no longer be able to buy an ISDN line ad as of 2025 any technology using an ISDN connection will no longer work. The switch off will mainly affect legacy phone systems using PSTN / ISDN however CCTV, alarm systems, telecare devices, fax and even lift services will also be affected.

The switch off was announced in November 2017 and already two trial sites have had their PSTN switched off. Between 2022 and 2023 we’ll see over 5 000 exchanges stop sell, meaning they will no longer be able to sell ISDN lines.

The target for the full national PSTN switch-off is December 2025.

PSTN & ISDN are being switched off, there’s no avoiding it. So, making the switch now means that you get to enjoy all the benefits of moving over to a modern technology solution sooner.

  • Cash in by reducing your costs now, not in a few years time
  • Benefit from better call features and anywhere comms
  • Improve your customer experience
  • You’ve got to do it anyway, so why wait?

What are the benefits of moving from PSTN and ISDN?


Lower costs

SIP Trunking and cloud telephony are both more cost-effective, usually including minutes in a single monthly cost.

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Hybrid working

Cloud Telephony supports hybrid working, enabling you to make and receive calls from anywhere on any device.

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Improved experience

Both SIP and Cloud Telephony are feature-rich and will help you provide a far superior customer experience.

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Quick installation

SIP and Cloud Telephony can both be installed remotely and enable you to keep your existing phone numbers.

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Grows with you

SIP and Cloud Telephony allow for easy scalability which enables your technology to grow with your business.

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What are my options when switching from ISDN?

There’s two main communication solutions to choose from when switching over from PSTN and ISDN.

Businesses need to evaluate their options for moving towards modern digital comms. Currently, there’s two main technologies that are both superior to ISDN.

SIP Trunks

With SIP Trunking you can route calls over your business internet connection at lower costs. This is the choice for you if you’ve recently invested in an on-site PBX or just want to keep what’s familiar while also gaining access to enhanced capabilities.

  • Cheaper call and line costs
  • Lines can be quickly and easily added
  • Calls can be easily re-routed
  • Greater resiliency over ISDN
  • Keep your current handsets and PBX system
More on SIP Trunking

Cloud telephony

VoIP cloud phone systems provide advanced calling features and an easy way to answer calls on-the-go on any device. Choose Cloud Telephony if you want to move your communications fully to the cloud and have no on-site hardware to maintain.

  • Cheaper call costs and no hardware maintenance costs
  • Enables anywhere, any device calling for remote working
  • Users can be quickly and easily added
  • Calls can be easily re-routed
  • Includes a vast range of call features
  • Facilitates unified communications
More on Cloud Telephony
The Big Switch Off

‘The Big Switch Off’ guide

Switching from PSTN and ISDN doesn’t have to be expensive or stressful, we can help manage every facet of your transition. Our guide takes you through all of the benefits of moving away from your legacy tech and why switching now can benefit your business.

Download guide
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The National Domelight Company says goodbye to ISDN

They moved away from ISDN and switched to future-proofed phone solution to help them work remotely, be productive in any location and provide a better experience to their customers. Have a read to see how we helped them achieve this.

View case study