Multicolour phones

The End of ISDN Lines

In 2023 BT are ending the provision of ISDN/PSTN lines and by 2025 these networks will have been turned off, meaning businesses will have to move their telecommunications solution to a VoIP telecoms solution. However, as Telephone Exchanges reach 75% FTTP capacity Openreach plan to bring their Stop Sell Notice forward. Rainbow expects that these notices will start to be issued in Northern Ireland from June 2021.

Why are ISDN Lines Being Turned Off?

ISDN and PSTN lines have delivered voice services for many years, but as new technologies have evolved these lines advantages have been eroded and the costs of maintaining these legacy networks is no longer effective.

What is VoIP?

Voice over Internet Protocol (VoIP) delivers all the benefits of ISDN/PSTN lines, whilst offering huge savings, additional functionality, higher resilience and greater flexibility; by sending voice traffic securely over the internet in digital packets.

Watch our short video to learn more.

Moving from ISDN to VoIP Telephony

There are two options when choosing the replacement of your traditional lines, these are SIP and Hosted. The right option will depend on your current business telephony set-up, future plans and internet connectivity.

Digital Phone Line

A digital phone line delivers both voice and data over the internet connection. It’s a simple form of VoIP.


SIP telephony replaces the traditional lines going into your existing phone system, with an  internet connection(known as a SIP Trunk). SIP telephony enables to continue to utilise in your PBX whilst adding additional functionality and capacity through the internet connection.


Hosted telephony removes the need for a physical phone system, as everything is hosted in the cloud, creating a virtual phone system. Hosted telephony enables you to benefit from all of the functionality of a premium phone system, whilst enabling you to access your calls via any connected device and connect office locations effectively.

Do I need SIP or Hosted?

What should I do?

Once you have decided to consider a move to VoIP talk to us about your options. We can explain your options depending on your individual business requirements and what your aims are.

However with the end of ISDN lines, you should consider the following when choosing a VoIP communications partner:

  1. Is the solution carrier grade?
  2. Does the solution have ISO accreditation for data security and business continuity?
  3. Does the solution provider offer adequate aftersales support?
  4. Does the solution fit with your business now and in five years time?
  5. Have you looked at both SIP and Hosted Solutions?

Why Choose Rainbow Communications

Rainbow has extensive experience in deploying both SIP and Hosted solutions, enabling us to guide you to the right solution for your business and deliver a seamless transition from your legacy ISDN/PSTN lines to VoIP telephony.

Rainbow’s largest deployment of VoIP services was for the Northern Ireland Civil Service, where we moved approx 55,000 direct dial numbers over 155 sites from their legacy network to a VoIP service.

Call us now and find out more