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PSTN Switch Off: TelXL customers will see a seamless transition

Our national analogue PSTN and ISDN networks will no longer be around from 2025 as the UK moves to a fully digital network infrastructure.

In this article, we outline what this will mean for businesses, why it is happening and happily report that TelXL’s customers will not be affected.

We cover:

What is the PSTN?

We might think of the ‘Public Switched Telephone Network’ PSTN merely in terms of the network of cables that carry phone calls. However, it subsumes optical fibre, cables, copper telephone lines, microwave links, exchanges and even satellite links, with an array of supporting hardware and software, to transport telephone calls and other data around the country.

In 2006, Openreach was formed to provide fair access to the national network for communication providers and creating competition against the incumbent BT. Today’s PSTN supports several products that are routinely bought by the majority of communication service providers – in the form of Wholesale Line Rental (WLR) or Integrated Services Digital Network (ISDN) propositions – which are bundled into propositions and resold to both consumers and businesses.

The PSTN also carries more than just voice-telephony calls: It connects alarms, electronic point-of-sale (POS) machines door entry systems, CCTV, faxes and telehealth alarms.

However, over the last few decades, telecommunications operators have continuously built faster and higher-capacity networks based on internet protocol (IP) which can support both telephony and data. While these networks could not provide the quality of service required by telephony calls for a time, they have now reached a point in their evolution where they can, which renders the old PSTN network surplus-to-requirements.

What is the PSTN “switch off”?

The “switch off” includes the decommissioning of the entire PSTN network, such that the services it supports will simply no longer work. By the end of 2025, BT have said that, “every phone line in the UK will be digital, routing calls over IP (Internet Protocol) rather than the traditional PSTN.” The same goes for the various other non-voice devices connected to the PSTN. There will be no exceptions.

The knock-on effects also extend to several broadband services, including Asynchronous Digital Subscriber Lines (ADSL) Broadband and Fibre-to-the-Cabinet, which both rely on the underlying physical phone line and WLR service.

Although the target-date for the switchover represents a hard cut-off, the PSTN has already been transitioning for many years. The growth in broadband internet has seen the PSTN upgraded to keep pace for over a decade, creating a core network that is now largely digital.

Even before BT’s announcement, ISDN lines have not been installed in Central London since 2014. BT first announced that it was to close the PSTN back in November 2017. In 2018, Openreach announced their “Fibre First” strategy and vision of the future-orientated replacement network, unlocking the huge capacities and speeds of optical fibre. In 2020, a five-year reminder was given that WLR was being withdrawn.

From June 2021, BT stopped selling ISDN products at the first tranche of exchanges. The aim remains to completely withdraw ISDN and PSTN services by the end of December 2025.

The “switch off” of the PSTN represents a fundamental and ubiquitous step-change to the UK’s communications infrastructure: a true ‘end of an era’ event, arguably equivalent-to or even exceeding the relevance of the moment that analogue TV ended in the UK in 2015.

Why is it happening?

The requirement for a separate fixed-line analogue network has simply diminished, as the parallel digital network has become faster and more reliable. Over time, the digital IP network gradually became able to telephone calls via VoIP or SIP lines to the necessary high levels of quality and reliability.

Meanwhile, the PSTN has become older and harder to maintain, which has become a concern for operators. Continuing with the PSTN would potentially see price rises and poorer services if it was maintained into the future. BT envisage being able to make considerable savings by turning it off.

Digital networks will offer a raft of further capabilities to consumers and businesses, which contribute sources of value to the UK’s wider digital strategy, including supporting new emerging services, such as those related to 5G and the internet of things.

Although 8 in 10 UK households still owns a landline, usage has dropped considerably with many now preferring mobile or various messaging apps. Only 4% of households have a landline and no mobile. Businesses have moved to VoIP products and use tools like Teams and Zoom to communicate with colleagues, customers and suppliers. Such services tend to offer far more features than merely the call itself.

What does it mean for businesses?

After the PSTN is switched off, the services carried on the network will simply no longer work. This can, in extreme, create an existential risk.

However, this is a moment of opportunity for many businesses. The alternatives to the PSTN, in the form of SIP and VoIP both offer additional benefits and are generally cheaper:

SIP services are where part of an internet connection is partitioned off and dedicated to carry voice calls.
VoIP services are where calls are carried over an internet connection. Features with VoIP calls include call recordings, voicemail, and the very strong benefit of being able to access the service from traditional phones, mobiles, tablets or desktops.

Upgrades to existing services also become easier, because the digital architecture negates the need to change physical infrastructure. As businesses change in size and requirements, then digital services will be able to flex with those requirements much more readily.

For the short term at least, Openreach will be offering an alternative to its ADSL and fibre broadband services, called “Single Order Generic Ethernet Access (SOGEA)” to replace their ‘fibre to the curb’ offering. “Single Order Transition Access Product (SOTAP)” will be Openreach’s broadband only ADSL replacement, available only in locations where fibre is not available.

How do businesses need to prepare?

BT have outlined essential steps that businesses need to do:

  1. Upgrade to high quality internet connectivity, so that It has the capacity to handle services now and in the future.
  2. Audit the uses of the phone line – ensure it is not being used by faxes and alarms etc. If it is either change the device to an “IP Mode” operation if possible, seek an upgrade from the service provider or use a conversion adapter.
  3. Educate employees on the possibilities of digital services, by distributing user guides and other information.
  4. Consider opportunities to get rid of hardware. For instance, it may be timely to consider moving to an phone system which users IP headsets and softphones.
  5. Plan for changes to the approaches to communications: Digital systems allow for integration of mobile apps, for instance. They are a better enabler to remote or hybrid working, as but one application.

What does it mean for TelXL customers?

We are pleased to say that there will be no risks to TelXL customers’ telephony services!

Communication providers are expected to ensure that the change runs smoothly for customers.

At TelXL we are ready to support our businesses on their transition, by offering a seamless experience at the point the PSTN switch off. This is aside the high levels of resilience our telephony networks offers, which mean were are trusted by organisations in the public and private sector, for whom communications are mission-critical.

For resellers who look after customers who are also unsure of their risks, we are delighted to also assist.

Through our bespoke communication solutions, we also offer businesses creative ways to get around any esoteric challenges they may face, so as with analogue alarms and devices that are part of their network.

Contact us to talk more about reselling our products and also how we can help you overcome any business continuity concerns post the switch-off and beyond.


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