BT to Switch ISDN Network off by 2025

BT have announced that by 2025 their ISDN network will be switched off. But what is ISDN, what does the switch off mean, and how will it impact your business?

ISDN stands for the Integrated Services Digital Network and comes in two forms: ISDN2 (allows 2 channels per line) and ISDN30 (allows 30 channels per line). The switch-off of ISDN means that businesses whose phone lines use ISDN will no longer be able to do so and will have to use a different service.

So what do BT have planned for phone systems using ISDN?

BT hope to move business telephone lines onto VoIP systems.

Voice Over Internet Protocol is the general term for any voice channel travelling over the internet, and is much more flexible than ISDN. Many companies are already using VoIP technologies as their popularity continues to increase.

Are there benefits to using VoIP?

YES. Below we’ve listed a few reasons why VoIP could enhance your business’ performance and lines of communication.


Phones systems using ISDN can be restrictive. Typically, only phones in your building are able to access contacts which means that if you or an employee can’t make it to the office through illness or weather – then you will have to use your mobile or personal landline to contact business numbers. In a VoIP setup, mobile phones can log in to your business’ phone system without being in the building. Your employee simply taps into their extension number to continue working and it won’t cost them, or you, an extra penny. They can even plug in ‘soft phones’ (handsets or headsets) to immediately connect to their work phone- irrespective of their location- as long as they have an internet connection.

Freedom of location

As long as you can access the internet, you can access VoIP. Which means it will easily work in any location around the world. If you have multiple branches all over the UK, or World, your employees can contact each other worldwide by dialing extensions.

Disaster recovery

If existing ISDN systems go down then automatically your phone lines will go down. This inconvenience can be annoying, frustrating and could even lose you business.

With VoIP your lines are virtual and can be carried over any internet connection in any location. So you can move your office phone line with you as you move, using any internet connection in any location and your customers won’t notice any difference.

Lower costs

With most businesses today having internet connections, VoIP can help you save on utility bills. In essence VoIP does away with telephone bills – if you pay for your business internet connection, you can use this connection to put all your calls through the internet- with no additional call costs.


With ISDN30 if you want to have more than 30 channels you will have to ask your supplier for a new telephone line to be installed. The process doesn’t come cheap and can be timely. On the other hand, if you have ISDN30 but only 10 employees, you’re more than likely paying for 20 lines you aren’t using.

With VoIP you can have as many channels as your internet bandwidth can handle – and you will only pay for what you use.

Why wait?

With this level of flexibility and cost savings from using VoIP, NI businesses are missing out on considerable savings and convenience if they don’t switch before the 2025 ISDN deadline. Talk to us today on 028 9032 8888 to learn more about your options and moving away from ISDN!