Alarm signalling after the PSTN switch-off
What fire and security alarm installers need to know about the January 2027 deadline, and how to migrate your customers to standards-ready IP signalling without disruption.
What is the PSTN - and why does it matter for alarm signalling?
The Public Switched Telephone Network (PSTN) is the UK’s legacy copper-wire telephone infrastructure. It has underpinned traditional landline calls, fax transmission, ISDN circuits, and critically for our industry, the vast majority of alarm signalling connections for over a century.
For fire and security installers, PSTN and ISDN lines have long been the default transmission path for alarm signals and CCTV from premises to Alarm Receiving Centres (ARCs). When those lines go dark in January 2027, any alarm panel or CCTV system still dialling out over PSTN will go silent.
PSTN & ISDN: What does it mean?
PSTN (Public switched telephone network)
The copper-wire analogue telephone network operated by Openreach. The backbone of UK telephony since the 19th century - and will be permanently retired in January 2027.
ISDN (Integrated services digital network)
A digital upgrade built on top of the PSTN infrastructure. Introduced in the 1980's. Because it relies on the same copper network, the ISDN is being switched off on the same date as the PSTN.
PSTN vs ISDN - What's the difference?
The PSTN carries analogue voice signals. The ISDN carries digital data and voice over the same copper wire at higher speed. For alarm signalling purposes both technologies face the same 2027 end-of-life and both require the same migration action.
Make sure that you are fully prepared for the PSTN shutdown
PSTN switch-off: Your step-by-step readiness guide
How does the PSTN work - and why is it being switched off?
The PSTN routes calls by establishing a dedicated physical circuit between two endpoints across a network of copper wires and telephone exchanges. When an alarm panel dials an ARC over the PSTN, it holds open a circuit for the duration of the signal transmission, a process called circuit switching.
This technology was reliable for its era, but it is ageing badly. Openreach has reported that PSTN incidents increased by 20% in 2023, with a 60% increase in hours lost by customers on the network in that same year. Maintaining two parallel networks, copper and fibre, is neither economically viable nor technically sensible for Openreach, which is why the retirement date is firmly set.
IP-based alternatives replace circuit switching with packet switching, transmitting data in discrete packets over broadband, cellular, or dedicated network paths. For alarm signalling, this means faster, more resilient, and more auditable transmission with no dependency on ageing network infrastructure.
PSTN switch-off timeline: What has already happened?
This is not a future event, the migration is already well underway. Many of your customers’ sites may already be affected by stop-sell restrictions.
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2020: Openreach announces retirement
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Sep' 2023: New PSTN and ISDN orders halt in over 100 exchange areas. No new lines can be ordered in affected areas. New ISDN orders end nationwide.
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May 2024: BT Group announces a delay to January 2027 to allow more time for complex migrations, particularly for telecare and vulnerable users.
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Now: Over 1,281 telephone exchanges covering 12.5 million premises are now under stop-sell. Openreach confirms January 2027 is "locked-in"
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2026: Peak demand for migration services. Installer availability and number porting capacity will be under pressure. Act now to avoid any bottlenecks.
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Jan' 2027: Every remaining analogue phone line and ISDN connection permanently stops working. Any alarm system still signalling over copper will fail silently.
What stops working in January 2027?
For fire and security installers, the impact goes well beyond telephone handsets. Any system using a PSTN or ISDN line as its signalling path will fail, silently, and without warning, the moment that service is upgraded or the exchange is decommissioned.
Are you fully prepared for 2027?
Download the guide
Critical risk for installers
An alarm system that fails to signal because its PSTN line has been withdrawn is not just a compliance issue, it is a liability issue. Duty of care obligations, insurance requirements, and monitoring contracts may all be affected if signalling paths have not been migrated in advance of the switch-off.
AddSecure alarm communications: Built for the post-PSTN world
AddSecure alarm communications solutions are designed from the ground up for IP and cellular alarm transmission, fully independent of the PSTN and ISDN infrastructure being retired. Our platforms are compliant with current alarm transmission standards and ready for the requirements of a digital-first signalling environment.
For installers, this means a proven, standards-ready migration path for every site on your books, with the resilience, redundancy, and auditability that modern installations demand.
Encrypted IP transmission
Secure, encrypted alarm signalling over IP networks. No reliance on copper or legacy switching infrastructure.
Dual path resilience
Primary IP path with automatic cellular failover ensures signalling continuity even during broadband outages.
Third party certified by LPCB
Meets EN50136 and graded to the transmission security requirements of BS EN50131 - ready for current and forthcoming standards.
Fast migration
Drop-in communicators designed for straightforward retrofit to existing panels, minimising site disruption during migration.
Installer portal
Manage, monitor and audit your entire installed base from a single dashboard. Full remote diagnostics and status visibility.
ARC integration
Direct integration with major UK Alarm receiving centres. No change to monitoring contracts required in most cases.
Your 5-step PSTN migration plan for installers
Identify every site you maintain that currently uses a PSTN or ISDN line for alarm signalling. Include fire, intruder, CCTV monitoring, and any other system with a telephone-based transmission path. Many installers discover lines they had forgotten about during this process.
Check your sites against the stop-sell map: Openreach's stop-sell programme is already active across 51% of UK exchanges. Some of your customers' sites may already be unable to order new or replacement PSTN services. Use Openreach's checker to identify which exchanges have already been migrated. Or speak with your customer to see if they have had any migration notifications.
Assess the right signalling solution for each site: Not every site has the same connectivity. Assess whether IP over broadband, cellular (4G/5G), or a dual-path combination is the right solution for each premises based on available infrastructure, grade requirement, and risk profile.
Plan the migration in priority order: Ideally prioritise sites in stop-sell exchange areas first, then high-grade and critical-risk sites. Avoid leaving migration until the last minute, but time is running out , start your upgrades now. Installer capacity and equipment supply will be under significant pressure as the deadline approaches.
Notify customers and update maintenance contracts: Document all migrations and update your maintenance agreements to reflect the new signalling path. Ensure customers understand that the change is a legal infrastructure requirement, not an optional upgrade, this simplifies sign-off and budgeting conversations.
Installer FAQs: The PSTN switch-off and alarm signalling
Will the PSTN switch-off happen in January 2027?
What happens to an alarm system if the PSTN line is withdrawn and hasn't been migrated?
Can I just use a broadband connection instead of the PSTN line?
My customer's site already has fibre broadband, are they automatically compliant?
What is the difference between the PSTN and ISDN for alarm signalling purposes?
How long does a migration typically take per site?