book and pen

PSTN and ISDN Lines Switch Off

The 2025 PSTN and ISDN line switch off is getting nearer so it’s important to know what is coming and what you need to do.

Lines Recap

BT previously announced that they would be switching off PSTN and ISDN lines in 2025. As the Public Switch Telephone Network (PSTN) is aging and as broadband services have improved, there has been a change to a more digital network. Read our previous post here.

  • PSTN – Public Switch Telephone Network – referred to as ‘traditional telephony’ and allows calls to be made over copper lines.
  • ISDN – Integrated Services Digital Network – available as ISDN2 or ISDn30 and supports channels in pairs. One channel provides one concurrent call at a time.

The PSTN supports ISDN and other services such as Wholesale Line Rental (WLR). Connectivity products like Asymmetrical Digital Subscriber Lines (ADSL) and Fibre to the Cabinet (FTTC) rely on WLR so will be impacted when WLR goes end of life. Another reason for this change is the development of Voice Over Internet Protocol (VoIP). Openreach will now focus on developing the fibre network rather than offering voice services.

Therefore, if you need voice services, you will now need to consider migrating to SIP or having a hosted PBX system. At Gower, we’ve been installing SIP based phone systems for many years and have recently partnered with Wildix. There by offering a complete browser based phone system. Learn more about Wildix here.


The Salisbury Exchange has already withdrawn services (started 01-12-20) and the Mildenhall Exchange starts 04-05-21, both of which are part of Openreach’s trial. In addition, starting from September 2023 all exchanges will have WLR withdrawn. This is known as stop sell.

Products impacted by stop sell means the following will no longer be able to be processed:

  • > New supply,
  • > Line takeovers,
  • > Start of stopped lines,
  • > Migrations or Communication Provider transfers,
  • > Addition of broadband to copper voice lines,
  • > Modification of bandwidth or the addition of lines and channels to existing installations.

As you can see from the image below, in June this year, BT will start to reduce the availability of analogue phone services. This is part of their phase out over the next 3 to 4 years.

lines switch off timeline chart
click image to make full screen

Replacement Lines

Openreach will offer Single Orders; a variant of ADSL or Fibre. And as mentioned above, voice services would need to be ordered separately.

  • FTTC or VDSL (very high speed DSL) will be replaced by Single Order Generic Ethernet Access (SOGEA)
  • ADSL will be replaced by Single Order Transition Access Product (SOTAP)

Fibre to the Premises (FTTP) and Leased Lines (also known as ethernet) will not be affected by the switch off as these do not rely on a copper connection.


This will be the biggest change to telephony in many years and it’s important for businesses not to lose their calling capabilities. Therefore, we advise you to look at your current setup and make enquiries now. We’re open Monday to Friday, 9am to 5pm to take your call. Alternatively, use our contact form here to send us your questions.


Links open in a new tab

Openreach product breakdown –

Openreach stop sell –

Draytek ‘The End of Analogue Phone Lines’ –