All you need to know about the BT ISDN switch off

All you need to know about the BT ISDN switch off

We know that the BT's ISDN and PSTN switch off is coming in 2025. Here’s everything you need to know about what’s happening, when and why.

What’s happening to the telephone network - a timeline

The announcement of the closure of the ISDN and PSTN networks in 2025 goes public. 

Salisbury becomes the first UK town where ISDN and PSTN lines are no longer available for purchase.

2021 (May)
As the trial expands, Mildenhall follows Salisbury - no new ISDN and PSTN lines are available. 

An additional 117 exchanges are upgraded to faster FTTP (full fibre) connectivity, and no new PSTN and ISDN lines are available within their footprint.

In Salisbury and Mildenhall, WLR (Wholesale Line Rental - including PSTN and ISDN) is withdrawn entirely. 

WLR (including PSTN and ISDN) is no longer sold in the UK.

2025 (December)
WLR is withdrawn nationally, with all voice calls now over IP voice services. 

Why it’s happening - in numbers

The fact is that legacy systems like ISDN and PSTN are simply not designed for the kind of data-rich communications that are increasingly crucial to modern business.

6 - 8
The number of different collaboration tools now available to the average worker, from voice and video to chat and more.

The percentage of employees who say better communications would make a big difference to their success.

The percentage of chief marketing officers reporting improved team productivity after a move to more agile technologies.

The percentage of employees who today work away from their main office 2.5 days per week. 

That’s when the current ISDN network was introduced. It’s reaching the end of its life.


What are the alternatives? 

There are plenty of alternatives to ISDN, all of which have benefits for your business. Here are the terms you need to know.

IP Voice
The general term for voice services that work over broadband.

Voice over Internet Protocol (VoIP)
A service that lets you make voice calls over a data network.

SIP Trunking
The IP voice equivalent of ISDN, letting you use data and voice services at the same time. 

Hosted Voice
Similar to SIP Trunking but puts all the infrastructure in the cloud instead of using on-site PBX hardware.

Unified Communications
Services that combine voice with a range of other multimedia services, like video, chat, SMS, email and presence.