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Small changes needed – The end of ISDN


April 24, 2019


June 28, 2023


The end of ISDN and PSTN circuits isn’t as far away as you might have previously thought. In fact, BT Openreach announced that starting in the year 2020, businesses and individuals in the UK will no longer be able to purchase ISDN lines.

This news follows BT’s previous promise to discontinue ISDN and PSTN circuits entirely by 2025 (telcos in other countries, like Deutsche Telekom, have vowed to phase out ISDN even sooner.) Granted, this timeframe seems well into the future, but forward-looking organizations need to make SIP migration a priority now.

Why is BT getting rid of ISDN/PSTN circuits?

Modern technology has far outpaced the capabilities of traditional ISDN PRI and PSTN circuits and has prompted a growing number of businesses to abandon their dated telephony systems in exchange for faster and more agile networks.

From BT’s viewpoint, it is simply too costly and counterproductive to continue to manage and support multiple legacy networks. Converging each of their services into a single, all-inclusive network is the logical thing to do.

Benefits of SIP trunking

This is the time for businesses to really start to consider the tremendous benefits of SIP trunking and what it can do to help them not only streamline their communications expenditures, but also optimize their existing resources.

The true advantage of SIP is that it eliminates the need for a physical phone line completely—which means fewer limitations around location, call volume, and cost savings. It also means your business doesn’t have to invest in expensive infrastructure to get started and you can get setup faster.

Moreover, since SIP phone lines are ‘virtual’, employees can now reap the benefits of true flexibility—working whenever or wherever they need, provided there is access to an Internet connection, unlike legacy systems that restrict communications to the reach of a physical ISDN line.

This doesn’t even begin to account for the growing list of operational benefits:

  • Businesses can keep their existing phone number
  • Quickly establish a local presence in the places where you do business
  • Tangible cost savings on calls, call routing, and connectivity
  • The need for expensive ISDN maintenance is completely removed
  • A single, optimized network for both high-quality voice and data

2025 seems like forever, but it’s already less than four years away. So, if your organization’s existing ISDN or PSTN contract is up for renewal in the next couple of years, you’ll need to start considering how SIP and VoIP technology can benefit your business.


Modern, cloud-based SIP services offer businesses the platform for global reach, improved customer engagement, and the ability to execute on their digital transformation strategies.

Communications-as-a-Service (CaaS) is evolving the SIP trunking market beyond simple PSTN access. If you’re interested in how you can read about the benefits they’re bringing to businesses in our recent Nemertes Research guide.

If you have the right technology in place, you’re not only future-proofing your business, you’re also optimizing processes, improving performance and increasing both employee and customer satisfaction levels—It’s a win-win.

If you’re interested in ditching your ISDN circuits, contact us to see how Bandwidth’s SIP solution can provide you with better call quality at a fraction of the cost, all in the most important markets across North America, Europe, Asia Pacific, and beyond.

On the other hand, if you’re looking to learn more about SIP trunking and getting global PSTN access without the cost, take a look at a recent blog by Nemertes Research VP and Service Director, Irwin Lazar.