Is Your Alarm Still Working? PSTN Switch-Off Guide

Key takeaway

If your monitored alarm still depends on PSTN, legacy Redcare-style signalling, or an older mobile communicator, the panel can look healthy while the signal path has failed. Ask for written confirmation of how the alarm communicates, who receives the signal, and what backup route protects it before January 2027.

Here is an uncomfortable question.

When did you last have confirmation that your intruder alarm or fire alarm monitoring is actually communicating with the Alarm Receiving Centre?

Not "the alarm tested fine last month." Not "it went off when I triggered it." But confirmation that the signal pathway from your building to the monitoring centre is intact and functioning right now.

If your system relies on an old BT landline or a legacy signalling service to communicate, there is a real possibility the answer is: you do not know. And in some cases, the system has already stopped communicating entirely.

This is not scaremongering. It is the direct consequence of three overlapping changes to UK telecoms infrastructure that have been rolling out for several years and are now, in 2026, arriving at their most critical phase.

What Is the PSTN and Why Does It Matter for Your Alarm?

The PSTN (Public Switched Telephone Network) is the analogue copper telephone infrastructure that has underpinned voice and data communications in the UK for well over a century.

It is estimated that around four million fire and security systems in the UK communicate to Alarm Receiving Centres using the PSTN network. That is a significant number. And the network those four million systems depend on is being switched off.

The PSTN is failing due to a lack of parts and, increasingly, environmental factors such as storms or heat-related faults. Ofcom reported that 2024 saw a 45 percent increase in the number of PSTN incidents reported.

Openreach says the analogue phone network will be retired by 31 January 2027. If a business alarm depends on an old copper service, the communication route needs checking before that date rather than after a fault appears.

Three Changes That Have Already Happened

The PSTN switch-off does not exist in isolation. It is part of a broader shift away from analogue infrastructure, and three specific changes are directly relevant to business alarm systems.

1. BT Redcare Closed in December 2025

This one matters most for businesses with monitored alarm systems, and it is the change that has caught the most people off guard.

BT Redcare was one of the most widely used alarm signalling services in the UK. Thousands of commercial fire alarms and intruder alarms used it to communicate activations to monitoring centres. BT Redcare operations closed in 2025, well before the final 2027 switch-off deadline.

If your alarm uses BT Redcare and you have not migrated to an alternative signalling solution, your system may look operational from the front panel. The alarm will still sound if triggered. But the signal to the monitoring centre, the part that actually calls for help, may not be going anywhere.

Your alarm is, in that scenario, a very expensive noise maker.

2. Older Mobile Signalling Is Being Withdrawn

Many alarm systems, particularly those installed or upgraded in the 2010s, were fitted with GSM communicators that transmitted alarm signals over older mobile networks.

Some legacy alarm communicators and wireless security devices still rely on ageing mobile technology. Some systems will not make it obvious at the panel when the SIM or mobile path has stopped communicating. This is one of the awkward causes of silent system failure in older monitored alarm systems.

Silent system failure means the system appears to work locally. It tests fine at the keypad. The sounder may activate. But the communication path, the part that connects the building to help, may not be doing its job.

Ask the installer to confirm the communicator technology, the active mobile network, the expected withdrawal risk, and whether a 4G, IP, or dual-path upgrade is needed.

3. The Digital Stop-Sell Is Already Active

In practical terms, in many exchange areas, the "stop-sell" is already active: meaning no new PSTN or ISDN services can be purchased, and no system takeovers or modifications involving PSTN lines are permitted.

This means that even if you wanted to maintain your existing PSTN-dependent alarm signalling, you may not be able to do so when it next requires modification or takeover by a new contractor.

What Does This Mean for Your Alarm System in Practice?

The practical implications depend on how your alarm system currently communicates. Here is a breakdown by signalling method:

Alarm Signalling Grades and Why This Matters for Your Insurance

Alarm signalling grades, designated DP1 through DP4, define how quickly a fault in communication between a business alarm system and the Alarm Receiving Centre is detected.

• DP1: Can take up to 25 hours to detect a path failure, now widely regarded as unsuitable for commercial premises.
• DP2: Detection in approximately 31 minutes: an improvement, but still leaves a significant exposure window.
• DP3: Communication failures detected within 4 minutes, the standard for most modern commercial systems.
• DP4: Detection within 3 minutes, the highest resilience grade.

Think about that from a practical standpoint. If your system is running DP1 signalling and the communication path fails at 9pm, you might not know until 10pm the following evening.

What Does a Compliant, Future-Proof Solution Look Like?

A modern, future-proof signalling solution for a commercial or industrial alarm system typically involves:

• Dual-path signalling over IP and 4G LTE: two independent communication paths, providing resilience against either path failing.
• DP3 or DP4 grade signalling: faster fault detection and better insurance compliance.
• A modern digital communicator: the legacy signalling device in your alarm panel will usually need replacing.
• Connection to a BS 5979 Category II compliant ARC: the benchmark for commercial monitoring.

What About Your Fire Alarm?

Everything above applies equally to fire alarm systems that use remote signalling to an ARC or to the fire and rescue service. If your fire alarm uses PSTN-based signalling, the same urgency applies. In some respects, it is even more critical.

Your fire alarm's signalling arrangements should be reviewed as part of your next annual fire alarm service visit at the very latest. If your system is due a service, raise this explicitly with your engineer or include it in your fire and security maintenance review.

Do You Actually Know How Your Alarm Signals?

A significant proportion of businesses have alarm systems that were installed or upgraded several years ago. The business owner knows the system is there, knows it is serviced, and assumes it is working. The specific signalling technology it uses, and whether that technology is still functional, is not something they have ever had reason to think about. That assumption is now risky.

If you are not certain how your system communicates with the monitoring centre, call your installer or maintenance contractor this week. If you do not have a maintenance contractor, that is a separate problem worth addressing, and one we can help with.

Contact FIDEC for a free assessment of your alarm signalling: 0333 3662 007 or info@fidecss.co.uk.

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