BT Announce End of ISDN and PSTN in 2025


As BT draws an end to ISDN/PSTN, you have until 2025 to find an alternative solution to your telephony and business internet requirements. They have stated that you can purchase ISDN lines up to September 2023 but, there will be a forced migration phase between April and December 2025.

What is a PSTN line?

“The public switched telephone network (PSTN) is the aggregate of the world’s circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication” – Source.

Your phone service provider owns and operates a circuit-switched phone line made up of copper wires which carry analogue voice data.

What is an ISDN line?

“Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network” – Source.

ISDN (Integrated Services Digital Network) uses digital transmission to provide voice services, over more than one channel. Unlike PSTN, ISDN technology allows businesses to increase the number of lines, or channels, to suit their demands.

What happens if I have ISDN?

Even though you have been given a few more years to be able to purchase more ISDN lines, it doesn’t change the fact that it is old technology and will soon be obsolete. We advise that if your telephony contract is up for renewal, you start reviewing alternatives.

Why are they doing it?

In the new world of communication, IP (Internet over Protocol) is the most logical step forward for businesses to take, so they are not investing any more time and resources into a technology that will not benefit businesses going forward.

What are my alternatives?

New fibre infrastructure has now become affordable and widely available for small businesses thanks to the recent investments in the UK communications network. IP based solutions such as VoIP and SIP are therefore the best alternatives for businesses.

SIP uses virtual phone lines instead of physical lines like ISDN. If you have an on-premises phone system, this is the best alternative. There are many reasons for this, including the flexibility it provides, the speed with which lines can be added or removed, the quality of the calls, and the lower call costs.

A Hosted IP phone system would be a good option if you have ISDN lines, but don’t want to commit or retain an on-premise phone system.

With a hosted IP phone system, you use your internet lines but effectively rent a phone system. This is a great solution for those who want the scalability and functionality of a phone system without having to pay additional maintenance fees.

What are the benefits?

  1. Huge savings – The cost of calls and line rental could be reduced by up to 78% compared to ISDN.
  2. Greater flexibility – Move anywhere in the UK and simply plug back into the network without changing numbers.
  3. Faster installation – By avoiding the need to have an engineer install physical lines, you can get connected faster.
  4. Higher resiliency – It is possible to install multiple fibre lines to give you failover and backup so you’re always connected.
  5. Advanced features – An array of new and advanced features is available with increased control, integration, and analytics.


Our all-digital phone system, Microsoft Office 365, allows for a better level of customer service. At the most basic level, you will be able to make and receive calls from any device, wherever you are, using the same number. By linking your business applications and systems with video chat, calls and collaboration, you’ll be closer to your customers and colleagues. All of this is possible as everything is in the cloud, so you can access systems anywhere, working from wherever you are.

By factoring in IP’s lower costs, it makes sense to go digital as soon as possible.

Get in touch with one of our experts today to learn more about switching.

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