COMMUNICATIONS: What is the PSTN switch-off? BT Urges UK Businesses to Embrace Digital Phone Networks

Phone lines and other analogue technology need to be ready for the big PSTN switch-off. We’re urging businesses to migrate off the aging PSTN to All-IP by the end of December 2025 to safeguard their services, well before the final shutdown of the network in January 2027.

What is the PSTN switch-off?
BTs existing traditional phone network is being replaced with a newer, shinier version.

Public Switched Telephone Network (PSTN) is an analogue, legacy platform using underground copper wires to enable communication. But this hardware can no longer sustain modern requirements and is become increasingly fragile and prone to failure. Ofcom’s recent Connected Nations report highlights that in 2024, the number of significant PSTN resilience incidents reported increased sharply by 45%.

Accordingly, BT are switching to a fully digital phone network using IP (Internet Protocol) technology. Every phone line in the UK will be digital, routing calls over IP rather than the traditional PSTN. Any remaining services not switched to the new digital network will be lost.

Alongside PSTN, Integrated Services Digital Network (ISDN) lines are being put to bed. In 1986, some older analogue landlines were replaced with ISDN, improving the service and adding features that weren’t available with the traditional telephone system. Although it was an upgrade then, ISDN is now outdated and unable to compete with IP technology.