The BT Openreach PSTN and ISDN 2025 Switch Off

What is the PSTN and ISDN Switch Off? -  The Public Switch Telephone Network (PSTN) is aging and will reach the 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) and Integrated Services Digital Network (ISDN).ISDN is available in two common variants: ISDN2 supports channels in pairs and you can have between 2 ISDN channels or 8 ISDN channels. ISDN30 is provided for larger business customers usually, with options to have between 8 ISDN channels and 30 ISDN channels on each service. A single ISDN channel will provide a customer with 1 concurrent call at a time. 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telephony, including fixed lines and services in the Public Switch Telephone Network (PSTN) will be switched off and withdrawn from service.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? – The Public Switch Telephone Network allows calls to be made over copper telephone lines and fibre telephone lines using analogue signalling and is known as “traditional telephony”. As broadband services have increased in reliability and quality over the past 10 years, the PSTN has evolved to support this change to an almost completely digital network using digital technology. This means there will no longer be a requirement for the majority of traditional fixed line telephony users for fixed-analogue services in the coming years and traditional fixed lines and calls will cease to exist. The priority for Openreach moving forward, is to maintain a high availability fibre first network, as a result their legacy infrastructure and equipment serving the PSTN is now ageing and becoming more difficult to maintain.

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. These products are commonly mentioned by providers when discussing the PSTN Withdrawal but most providers fail to mention the connectivity products which are using these services like Asymmetrical Digital Subscriber Lines (ADSL) Broadband and Fibre To The Cabinet (FTTC) Broadband which will be impacted the WLR End of Life project. This is because the underlying line product is being withdrawn, therefore there is no underlying WLR telephone service to support the broadband. 

Will Openreach provide the PSTN replacement products and services? – Openreach was created in 2006 following an agreement by the Office of Communications (Ofcom) and British Telecom (BT) to provide equal and fair access to the UK’s telephony network. Their WLR (including ISDN) telephone products, allowed Communication Providers (CPs) to offer their own telephone service without having to maintain the network themselves at a fair, regulated price. As technology has changed, and telephone services can now be provided over Voice Over Internet Protocol (VOIP), Openreach priorities have moved. Openreach are now focused on developing the fibre network and they will not provide the over the top VoIP lines that will be required to provide voice.

Moving forward, Openreach products will be a Single Order (SO) variant of ADSL or Fibre broadband services. These products will become known as; Single Order Generic Ethernet Access (SOGEA) which is Openreach’s Broadband only FTTC replacement. Single Order Transition Access Product (SOTAP), will be Openreach’s broadband only ADSL replacement, which be available in areas where fibre isn’t. These new broadband services require investment in equipment but can be purchased via communications providers such as Digital Wholesale Solutions. 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.

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.