Posted on: 11 Jan 2022

Customer Announcement: the PSTN/ISDN Switch Off

In 2015, BT announced it will be switching off the PSTN and ISDN in 2025, marking the biggest change in the telecoms industry for over 30 years, but what does the end of PSTN and ISDN mean?

What is ISDN and PSTN?

The Public Switched Telephone Network (PSTN) is the landline telephone system originally set up for analogue voice communication. It works by sending analogue voice data over a circuit-switched phone line made of copper wires. Before digital transmission was available PSTN was the most reliable method of making voice calls and the main carrier for internet activity across the world. 

The Integrated Services Digital Network (ISDN) allows for the digital transmission of voice, video and other services simultaneously, using the traditional PSTN network.

What is the PSTN and ISDN Switch Off?

BT released a statement in 2015 that it would stop taking new ISDN orders in 2020, with a view to switching-off and deactivating its ISDN network completely at the end of December 2025. They will be transferring their networks from analogue and digital to an IP network.

ISDN and PSTN are being replaced because they are now outdated systems that take too much time and money to keep running. By converging all services – voice, data, video, and broadcasting to the IP protocol, BT only has to maintain one network, not several.

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

The PSTN supports a number of Openreach products: In technical acronyms these are known as WLR3 analogue, ISDN2, ISDN30, LLU SMPF, SLU SMPF, Narrowband Line Share and Classic products. These products are generically referred to, as WLR (Wholesale Line Rental) products. When the analogue network closes in 2025 these products will no longer be available.

How and when will Openreach start withdrawing service?

Openreach will stop selling WLR products that are reliant on the PSTN from September 2023. They will then completely close the WLR platform December 2025. After this date WLR products will no longer be available.

As a Kings Secure Technologies customer, what does this mean to me?

With the end of PSTN and ISDN services approaching, it is our intention to stop selling PSTN devices such as Digi comms and Dualcom/any alternative device using a PSTN path by 31st March 2022. As a customer who has an existing monitored alarm with the Kings Secure Technologies group of companies, we advise you to check if PSTN services are available on your line for any planned service provider change (note: PSTN is being removed from new or existing line changes by some providers). If you are using a signalling device connected to a PSTN line, please contact your KST Account Manager or email [email protected] to discuss suitable signalling options that do not use PSTN in preparation of the 2025 deadline.