Are You Ready for The BT ISDN Switch-Off in 2025?

If you’re not already aware, BT is preparing to switch off its ISDN network in 2025 – here’s everything you need to know about the switch-off and how it will affect you.  

When BT initially announced the ISDN switch-off, it seemed like a lifetime away. However, with the deadline fast approaching, we wanted to fill you in with key information before the 2025 deadline.  

What is The ISDN Switch Off?  

In 2015, BT announced that it would be moving away from the preexisting ISDN analogue phone network by 2025.  

What Exactly Is PSTN and ISDN? 

PSTN stands for the Public Switch Telephone Network and is the traditional circuit-switched telephone network.  

Meanwhile, ISDN is short for Integrated Services Digital Network and is a digital platform which has been used since the 1980s to transmit voice, video and other types of data. 

Why is ISDN Being Switched Off?  

ISDN is a very old system, which makes it harder to maintain and use. With more modern systems available, ISDN struggles to compete and cope.  

Will I Be Affected By The Switch Off? 

Once the ISDN switch-off is completed, every home and business phone in the UK will be digital and will use VoIP (Voice of Internet Protocol).  

VoIP has been around since the mid-90s and converts your voice into a digital signal that travels via the internet.  

What Devices Will Be Affected? 

The ISDN switch-off won’t just affect phones, but also CCTV, alarms, door entry systems, fax machines and any other device connected to the ISDN network. 

How Do I Know If I’ll Be Affected? 

If you currently use an ISDN line, you will be affected by the switch-off. However, if you’re unsure whether you use ISDN, please contact us and we can advise you on the necessary steps to prepare.  

What Is Replacing ISDN? 

ISDN will be replaced by VoIP, which has been around since 1995. VoIP transmits voice and data through the internet, meaning that you only need an internet connection for your communications to work.  

What Are The Advantages of Using VoIP? 

There are many advantages of using VoIP over ISDN, including:  

  • Better call quality 
  • Integrated systems and devices 
  • Potential cost reductions 

Support With the 2025 ISDN Switch-Off 

We believe the ISDN switch-off is a good thing and will bring many new opportunities and advantages to businesses. 

Our helpdesk technicians are on hand to help you with your technical problems.  

If you’d like to discuss your telecoms or any other aspect of tech/business IT support, please drop us a line at or give us a call on 01225 426800.  

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