BT ISDN Switch Off

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In 2025, the UK government is set to phase out all ISDN and PSTN telecommunication networks. This shift is commonly known as the ‘BT ISDN Switch Off’ - a huge shift for companies using traditional phone systems. 

As a business owner, it's crucial to understand these changes and explore alternative options to ensure seamless communication for your company's growth.

Even though you have been given a few more years to be able to purchase more ISDN lines, we still advise that if your telephony contract is up for renewal you start exploring alternatives as ISDN is old technology and will soon be obsolete. 

BTT - ISDN Phaseout from BTT on Vimeo.

Why is ISDN being switched off?

The switch-off of ISDN is a result of the evolution of communication technology. BT recognises that IP (Internet Protocol) is the future, offering greater benefits to businesses. By discontinuing ISDN, BT can focus on investing in newer and more efficient technologies, making it clear that businesses should start considering alternatives.

What is replacing ISDN?

ISDN will be replaced with IP, so the first thing to do is look at whether your phone system is IP compatible:

  • If it isn’t compatible, then you need to invest in a newer model that is IP compatible.
  • If it is compatible, then you may wish to consider replacing your existing ISDN service with SIP trunking.

Switching to IP relies so heavily on the internet, which means you’ll also need to assess whether your internet connection is stable enough to support IP telecoms technology.

If your internet connection needs upgrading, it might be time to switch to a fibre optic connection or Ethernet-based leased line.

Embrace the Future: SIP and Hosted VoIP Systems

As the ISDN era comes to a close, businesses have two primary alternatives to consider: SIP (Session Initiation Protocol) and Hosted VoIP (Voice over Internet Protocol) systems. 

These options offer flexibility, cost-effectiveness, and scalability, ensuring that your business stays ahead in the competitive landscape.

You have a few options. The main two are SIP and Hosted VoIP systems:

SIP (Session Initiation Protocol)

SIP uses virtual phone lines instead of physical ones, offering significant advantages for businesses with on-premise phone systems. 

The benefits of SIP include:

  • Flexibility: Easily add or remove phone lines to match your business's changing needs.
  • Call quality: Enjoy superior call quality compared to traditional ISDN lines.
  • Lower call costs: SIP generally offers lower call costs, helping you save money.
  • Compatibility: In most cases, you won't need to replace your existing phone system, as many systems are compatible with SIP.

To find out more about SIP: click here

Take a look at our ISDN to SIP migration checklist: click here

Hosted VoIP (Voice over Internet Protocol)

For businesses that don't want to commit to an on-premise phone system, Hosted VoIP is an excellent solution. Hosted VoIP uses internet lines and offers the following advantages:

  • Scalability: Easily scale your phone system as your business grows without additional maintenance charges.
  • Cost-effective: Avoid the need for expensive hardware and maintenance, as the system is hosted by a service provider.
  • Remote work friendly: Enable seamless communication for remote and mobile employees.

Learn more about VoIP: click here

Read more about your alternative options: click here

Migration Made Easy:

Migrating to SIP or Hosted VoIP can be a smooth process with the right provider. You can typically retain your existing phone numbers, and the migration can take as little as three weeks, depending on the complexity and number of sites involved. The whole migration (depending on some factors like the number of sites) can take as little as 3 weeks.

Things to Consider During the Migration:

Before making the switch, there are some factors to consider. 

To help you prepare, check out our migration checklists: View our ISDN to Hosted Migration ChecklistView our ISDN to SIP Migration Checklist


    • What's available to replace PSTN for my business communications?

    Take a look at our range of IP-based options. You'll want to consider internet connectivity, cost, scalability, and integrations with your existing business tools. 

    • What is VOIP and how is it different from traditional phone services?

    VoIP (Voice over Internet Protocol) is an alternative to traditional telephone service. Using the internet instead of PSTN, it allows users to connect to other people using computers, smartphones, tablets, and even smart TVs.

    • Can I keep my existing phone numbers when I switch to an IP-based solution?

    Yes - you can keep your current phone numbers when you move to IP solutions. You can actually take those numbers with you wherever you move in the future, as they'll no longer be tied to specific areas.

    Speak to the Experts:

    If you're unsure about when to make the switch or need more guidance, our team is here to help. We offer free advice to ensure a seamless transition and future-proof your communication system.

    We’d be happy to give you some advice as to when you need to make the switch and any more considerations to make; as always, our advice is free.

    Contact us now: 0330 222 0330 | | Contact us page | fill out the form below

    As Always, our Advice is Free

    Need help deciding the best steps forward?

    We've been in the telecoms industry for over 26 years, so get in touch and an experienced member of staff will get in touch soon.

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