The Unheard Dial Tone: A 2026 Signalling Audit for UK Cameras and Intruder Alarms

A security system can fail without a red light, a siren or an obvious fault. In the UK, the retirement of the analogue telephone network and the closure of older mobile technologies has made that kind of quiet failure a practical risk for CCTV, intruder alarms and access control. The equipment may remain powered, the local recording may continue and the keypad may appear normal. What disappears is the path by which the system tells someone else that something has happened.

As of November 2026, the direction of travel is clear. Openreach has been retiring the public switched telephone network in stages, with stop-sell already applied across much of the country and full withdrawal scheduled for the end of January 2027. Mobile operators have also been switching off older generations of network. For owners of legacy security systems, the relevant question is not whether the change is coming. It is whether every signalling and remote-viewing dependency has been identified, tested and documented.

Why the dial tone matters

Many intruder alarms still use a telephone line to contact an alarm receiving centre. Some CCTV installations use a phone line or older mobile module for remote viewing, alarm uploads or health checks. Access control and door-entry systems may use similar paths for configuration or out-of-hours calls. These arrangements were once dependable because the copper line was ubiquitous and well understood. That assumption no longer holds.

A line that has been ceased may produce a fault indication on some panels, but not all. A SIM card attached to a decommissioned mobile service may fail silently until the next test signal. A broadband migration may leave a VoIP adapter unpowered after a power cut, taking the alarm path with it. The risk is compounded when the security system is managed by a landlord, managing agent or facilities contractor while the telephone account sits with another party.

Start with the signal path, not the box

The first step is an inventory, not a shopping list. For each system, record what it is, who owns it and how it communicates. This should include the intruder alarm panel and its communicator, CCTV recorders and remote-viewing services, access-control controllers, door-entry and intercom systems, environmental sensors and any lone-worker or personal alarm devices.

For each item, note the signalling medium: analogue telephone line, broadband, dedicated IP connection, 4G or 5G, or a combination. Record the network provider, the account holder, the SIM identifier where applicable and the alarm receiving centre account number. Note the polling interval, the test schedule and the last acknowledged test result. A system that has not been tested since a broadband change is not a tested system.

Primary, backup and the illusion of redundancy

Dual-path signalling is often described as resilient, but redundancy depends on diversity. Two paths that share the same broadband router are not diverse. Two SIMs on the same mobile network are not fully diverse either. A genuine backup should use a different medium or a different provider, and it should have its own power arrangements.

Check what happens during a mains failure. If the router, ONT or VoIP adapter is not on battery backup, an IP-based alarm path may collapse before the alarm panel's own battery is exhausted. Check whether the panel reports a line fault locally and remotely. Check whether the alarm receiving centre sees a missed poll. Ask whether the communicator is approved for the signalling method in use and whether its firmware is still supported.

Testing without creating a nuisance

Testing should be planned, not improvised. Use the alarm receiving centre's test procedure or the installer's test mode. Notify the receiving centre before sending test signals, and confirm that each signal is acknowledged. Record the date, time, signal type and result. Test remote viewing from outside the premises network, not from the same Wi-Fi. After any broadband, router or telephone change, repeat the test.

Do not rely on a single successful test. Where possible, test the primary path and the backup path separately. Confirm that the backup activates when the primary is unavailable, and that the system returns to normal afterwards. For CCTV, check that recordings continue locally during a communications outage and that remote access resumes without manual intervention.

Questions for installers and providers

Owners should ask for written answers, not verbal assurances. Which network does the communicator use? Is it dependent on a telephone line, a broadband service or a mobile network that is being retired? What is the migration route, and who is responsible for it? What are the recurring costs, contract terms and notice periods? Will the existing panel support the new communicator, or is replacement required?

For IP-based systems, ask about cyber hygiene. Is remote access protected by strong authentication? Are default passwords removed? Is port forwarding in use, and can it be avoided? For mobile-based systems, ask which network is used, whether roaming or fallback is available and how the SIM is managed. Ask for the asset register, the signal path diagram and the test log. These are not administrative extras; they are the evidence that the system is doing what it claims.

A migration plan that avoids panic buying

Migration should be prioritised by consequence. Monitored intruder alarms and any system protecting vulnerable people should come first. CCTV and access control can follow, but they should not be left until the line ceases. A sensible plan sets out the target technology, the responsible person, the budget, the expected downtime and the acceptance test. It should also cover records: retention of configuration data, camera credentials and alarm account details.

For landlords, managing agents and business premises, the plan should be shared with residents or occupants where appropriate. A security system is part of the building's operating infrastructure, and its communications dependencies should be visible to those who rely on it. Silence is not a neutral state. It is a failure mode.

The practical test for 2026 is straightforward. Can every camera, alarm and access-control system still reach the person or centre that needs to know? If the answer is uncertain, the audit is overdue.