The PSTN Switch-Off: What It Means for Your Alarm System
Last updated: 2nd June 2026.
The UK's analogue telephone network is being permanently switched off in January 2027. If your alarm system uses a phone line to communicate with a monitoring centre - or to dial out in an emergency - it will stop working when that happens.
This post explains what the PSTN switch-off is, which alarm systems are affected, what the consequences of doing nothing are, and what your options are for upgrading before the deadline.
Already know you need an upgrade? Book a free PSTN assessment with GMSE →
What is the PSTN switch-off?
PSTN stands for Public Switched Telephone Network — the traditional analogue phone network that has carried UK telephone calls for decades. BT Openreach is replacing it with a fully digital network, and the old system is being switched off permanently in January 2027.
When the switch happens, any device that relies on the old analogue phone line to communicate will simply stop working. For most people, the immediate concern is their landline telephone. But for a significant number of homeowners and businesses, the bigger concern is their alarm system.
What's the difference between PSTN and ISDN?
You may have seen older articles — including our own earlier post on this topic — referring to the "ISDN shutdown." ISDN (Integrated Services Digital Network) is a related but distinct digital telephone technology that is also being phased out as part of the same broader transition. Both PSTN and ISDN lines are being switched off, and both can be used by alarm communicators.
The term you'll see most widely used going forward is the PSTN switch-off — it covers the broader transition away from analogue and older digital phone lines.
Does the switch-off affect my alarm system?
Not all alarm systems will be affected — only those that use the phone line to communicate. Here are the signs that your system may be at risk:
Your alarm system was installed more than five years ago
Your alarm uses a telephone line to contact a monitoring centre
Your monitoring contract references a phone line or BT line
Your alarm panel has a phone socket connection
You have not been contacted by your current alarm provider about an upgrade
If any of these apply, your alarm communicator will stop functioning when the PSTN network is switched off in January 2027.
What happens if you don't upgrade?
The alarm panel itself may continue to appear normal — sirens and local alerts may still work. But the communication link to your monitoring centre will be silent. In the event of an activation, no alert will be raised and no response will be sent.
There are three specific risks for those who don't act:
Your monitoring centre won't be alerted. The communicator will attempt to dial out via the phone line — and fail. No one will know your alarm has been triggered.
Your insurance may be invalidated. Many home and business insurance policies require a working monitored alarm as a condition of cover. A non-functioning communicator could invalidate your policy at exactly the wrong moment.
You may not know until it's too late. The only way to confirm your communicator is still working after the switch-off is to test it — or to have upgraded before it becomes an issue.
What are the upgrade options?
The good news is that upgrading your alarm communicator doesn't necessarily mean replacing your entire system. There are three main paths:
IP communicator upgrade The most cost-effective option for most modern alarm panels. The communicator module — the part that dials out — is replaced with an IP-based unit that communicates via your broadband connection. The rest of the alarm stays in place.
4G communicator upgrade The communicator is replaced with a 4G mobile network unit. No reliance on broadband — ideal for rural properties or premises where internet connectivity is unreliable.
Full system replacement If your alarm panel is old, no longer supported, or due for an upgrade anyway, a full system replacement may be the most sensible long-term investment. Modern systems offer smart features including app control, remote arming, and push notifications.
Why act now rather than wait until 2027?
January 2027 may feel like a long way off, but there are three good reasons to act sooner:
Engineer availability. As the deadline approaches, demand for PSTN upgrade engineers will increase significantly. Those who leave it late may face longer waiting times and higher costs.
Avoid gaps in protection. Scheduling an upgrade on your own terms means your alarm remains fully operational throughout the transition. Waiting risks a period where your system is non-functional.
Insurance compliance. Some insurers are already asking for confirmation that monitored systems are PSTN-ready. Acting early demonstrates due diligence and keeps your cover intact.
How GMSE can help
GMSE Fire & Security provide free PSTN upgrade assessments for homes and businesses across Kent, London and East Sussex. We'll visit your property, identify your current communicator type, and recommend the most cost-effective upgrade path for your specific system.
For full details on the switch-off and our upgrade service, visit our dedicated PSTN switch-off page →
Or if you're ready to book an assessment: Get your free PSTN upgrade assessment →
Summary
The PSTN switch-off in January 2027 will affect alarm systems that use a phone line to communicate. If your system is affected and you don't upgrade, your monitoring centre won't receive alerts in an emergency — and your insurance cover may be at risk. Upgrade options are straightforward and don't always require a full system replacement. Acting now avoids the rush as the deadline approaches.