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What is the PSTN and ISDN Switch Off?

The Public Switch Telephone Network (PSTN) will reach its end of life in December 2025. The PSTN supports a number of Openreach products which Communication Providers (CPs) purchase at regulated pricing and often sell to businesses and consumers, wrapped up in their own line rental, broadband and call package deal.

These include Wholesale Line Rental (WLR), Shared Metallic Path Facility (SMPF) Broadband and Integrated Services Digital Network (ISDN). At the end of December 2025 traditional telephony, including fixed lines and services in the Public Switch Telephone Network (PSTN) will be switched off and withdrawn from service.

Why is Openreach withdrawing the PSTN and ISDN network in December 2025? 

Openreach is looking to maintain a high availability fibre first network, as a result their legacy infrastructure (traditional telephony) and equipment serving the PSTN is now ageing and becoming more difficult to maintain, prompting Openreach to withdraw its current product line by 2025.

Will Openreach meet the December 2025 Deadline?

Openreach are adamant the December 2025 deadline is set in stone. PSTN Lines that have not migrated to alterative services in April 2025 will be deemed as Orphaned Assets and Openreach intend to work with CPs to identify and migrate customers to alternative products by the December 2025 deadline.

What other lines and calls services are impacted by the 2025 closure? 

The Public Switch Telephone Network currently supports WLR, ISDN2 and ISDN30, Local Loop Unbundling Shared Metallic Path Facilities (LLUSMPF), Narrowband Line Share and Classic Products. This will in addition affect products such as Asymmetrical Digital Subscriber Lines (ADSL) Broadband and Fibre to the Cabinet (FTTC) Broadband. This is because the underlying line product is being withdrawn, therefore there is no underlying WLR telephone service to support the broadband. 

How and when will Openreach start withdrawing service? 

Openreach started withdrawing their services initially from their two trial sites Salisbury and Mildenhall.

The Salisbury exchange was used for the FTTP Exchange Project and follows the FTTP Exchange Rollout timeline while the Mildenhall exchange, is being used for the National PSTN Withdrawal and follows the National PSTN Closure timeline.

The Sailsbury Exchange started from 1 December 2020 and the end-of-life date for Salisbury is 16 December 2022.

Mildenhall Exchange began Stop Sell on 4 May 2021. This exchange will focus on a complete withdrawal of services by December 2022, even if no fibre is available.

Premises serviced by the Mildenhall Exchange will be replaced with SOGEA and SOTAP products and the communication provider will need to provide an over-the-top VoIP replacement service such as a hosted PBX system license or SIP Trunking.

There will be a stop sell point in September 2023, after which PSTN based products will no longer be available for new supply. By December 2025 all PSTN products will need to have been migrated across to replacement Single Order products.

What is the FTTP Priority Exchange Rollout?

The FTTP Priority Exchange Rollout allows Openreach to transition to alternative products earlier. When FTTP gets to 75% availability within a certain area, Openreach can designate that exchange as a Priority Exchange. At that point, a 12-month notice is given to stop the sale of copper-based products at premises where FTTP is available. If you want a new service or you want to switch suppliers, you will only be able to buy FTTP irrespective of whether you would prefer another service.

Openreach has been rolling out the FTTP Priority Exchange program in tranches, with a new tranche being announced every three months. Currently, there are four tranches, totalling 220 exchanges, which have been designated Priority. The first stop sell of copper-based products happens for 13 of those Priority exchanges in June 2021, with further stop sells in October, January, and April.

So, does that mean the FTTP Priority Exchange Rollout is happening earlier than the National Stop Sell?

In summary, there are two timelines to consider:

National PSTN Closure

  • Impacts every exchange in UK
  • Stop Sell of PSTN based products in September 2023
  • PSTN based products need to be migrated to alternative products by December 2025

FTTP Priority Exchange Rollout

  • Impacts individual exchanges
  • 12 months’ notice of copper-based product stop sell when 75% FTTP availability
  • Impacts customers from June 2021

This is an ideal opportunity to get ahead of the curve, as many people will only focus on the future 2023 Stop Sell date, while missing on the opportunities that are available today.

What other lines and calls services are impacted by the 2025 closure? 

Moving forward, Openreach products will be a Single Order (SO) variant of ADSL or Fibre broadband services.

These products will become known as; Fibre To The Premises (FTTP) and Single Order Generic Ethernet Access (SOGEA) which is Openreach’s Broadband only FTTC replacement.

When these Single Order (SO) broadband products are provided there will be no voice on the telephone line and no dial tone, this means the CP will need to provide some form of VOIP service like a Hosted PBX License or Session Initiation Protocol (SIP Trunking) service to provide the voice telephony element which would replace the traditional WLR or ISDN telephone line.

For a more in-depth look at the various products available follow our full breakdown here.

What are these alternative products that Open Reach has introduced? 

These alternative products fall into two categories:

  • All-Internet Protocol (All-IP)
  • Metallic Path Facility (MPF)


  • All-IP are a range of new products which are designed to deliver data only services, meaning they do not have a native ability to pass voice calls.
  • There is a range of All-IP products either currently available or in development including FTTP, SOGEA, SOGFAST and SOTAP. These are effectively data only versions of GFAST, FTTC and ADSL (their old-world counterparts). More details on these products can be found here. 
  • All-IP products are a data-only service, and if you want to make calls, you will need to purchase an over-the-top Voice over IP product (VoIP). If you wish to retain your telephone number, you will need to port it to the VoIP supplier.
  • If you use your current PSTN based service to make calls and want to continue to do so following migration to an All-IP product, then you will need to purchase an over-the-top VoIP service.
    • If you have an existing phone system you want to retain, SIP would be ideal for you. *Link to SIP
    • If you have simple voice requirements, then there are single voice line options designed to replace the old school analogue line.
    • If you are a larger business, a feature-rich cloud voice system would be preferable. *Link to cloud voice


  • MPF is an established technology, which came out of the deregulation or Local Loop Unbundling (LLU) of UK Telecommunications. LLU allows multiple telecommunications operators to use connections from the same local exchange.
  • The switch-off of the PSTN does not impact MPF services.
  • MPF services include Analogue Lines, ADSL and FTTC and have a native voice service included, so work with existing analogue handsets/wiring.
  • MPF removes a requirement to purchase an over-the-top VoIP product.
  • MPF is an alternative to SOGEA/SOTAP, in locations where FTTP is not available.

What will happen to Alarm lines, payment terminals and other special line rental services after 2025?

During the Public Switch Telephone Network closure, all these services need to be tested with new IP technology and the SO products. This means alarm line companies, payment terminals, traffic light systems, payphone lines, emergency pendants, dialysis machines, telemetry devices and any other special service must be tested by the equipment manufacturers. Openreach can provide line test facilities for testing equipment against their individual line configurations.

We strongly suggest that you should engage with your special service supplier at the earliest opportunity to start the conversation about how you protect yourself moving forward.

What does the 2023 Stop Sell date mean to me? 

From September 2023 Openreach will issue a full “Stop Sell” of new supply WLR. When we refer to new WLR there is further clarification needed on what would be considered as a new supply. For example, does this include a transfer to another CP?

As part of the nationwide PSTN, WLR and ISDN Withdrawal, from the end of September 2023 there will be no new line installations for both WLR and ISDN, including conversions of the WLR Line to an ISDN Line, increase of ISDN channels, change of address, start of a stopped line or working line take over.

Unsure of where to start with your PSTN 2025 strategy? Chess has a full range of PSTN switch off compliant services, and our consultative approach can guide you through determining the solution, which is best for you. Contact one of your experts for advice today.

About the author

Grant Thain

Grant Thain is an experienced Connectivity and Voice specialist. He’s undertaken a number of roles at Chess, and is now Vendor Alliance Manager. He supports Chess customers, vendors and people with his in-depth experience and knowledge of the solutions that are both available now, and under development.

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