Will the PSTN Switch-off Silence your Security Alarms?

UPDATED SEPTEMBER 2025

It goes without saying that security alarms need to be reliable. But how about future-proof?

As you’re probably aware, PSTN and ISDN services are to be switched off completely. The future of communication is IP, and analogue wiring will become obsolete for voice. Effectively, it’s the end of an era. No more analogue phone lines.

Most businesses realise that their phones may need an upgrade. Fewer are aware of the implications for their security systems.

PSTN lines aren’t just for phones. Older security alarms, lift emergency phones, CCTV monitoring systems, payment terminals and access control still send signals via PSTN lines. Unless an alarm system is enabled for IP or cellular signalling, no more PSTN means no more protection.

A quick rundown of PSTN, ISDN and IP

• PSTN (public switched telephone network) has been in general use since the 1800s. It uses underground copper wiring and circuit-switching to transmit analogue voice calls.
• ISDN (integrated service digital network) became widely used in the 1980s. Like PSTN, it uses the public telephone network but allows the transmission of data, voice, video and other services.
• IP (internet protocol) uses fibre optic cable and digital standards. It allows multiple devices to communicate reliably over local and wide area networks.

When is the Big Switch Off due to happen?

Originally, the Big Switch Off was due to be completed by December 2025. However, BT subsequently announced a delay until 31 January 2027. The reason for the delay? People just weren’t ready. They needed more time to adapt.

It’s also important to be clear: the copper wiring itself will not vanish overnight. Broadband services such as FTTC, ADSL and VDSL will still use copper in the short to medium term. What ends in 2027 is the analogue voice service that runs over those lines.

Why is it happening?

• Reliability, functionality and speed. In the digital age, we expect data to move instantly. The old analogue systems simply can’t cope.
• Security. Modern communications need encryption. Analogue lines can’t provide this.
• Cost. The PSTN and ISDN infrastructure is difficult and expensive to maintain. Fibre networks are more efficient and cost-effective.

 

The scale of the problem

There are still nearly 3 million PSTN-connected alarms in the UK. These include fire alarms, intruder alarms, CCTV surveillance, lift call buttons, access control solutions, and even some payment terminals.

Why is the Big Switch Off such a problem for alarms?

In short, alarm signalling. When an alarm is triggered, there needs to be a communications system in place to send an alert signal to the alarm receiving centre (ARC).

When they receive the alarm signal, ARC responders assess the cause of the alarm and take immediate action as appropriate.

If your alarm system is using the old PSTN line to connect with ARC, once the switch-off has taken place, the signal will not be transmitted or received. Without a communication system, the alarm is redundant. There will be no response.

Quite apart from the impact on the security of your premises and the safety of its occupants, this may well affect the validity of your insurance policy.

How to ensure your alarm system remains operational

Firstly, check whether your security alarms communicate with ARC via analogue lines. If security or fire alarms are more than 10 or 15 years old, they will probably be reliant on a PSTN-based system.

Some PSTN-based alarms can be upgraded, others will need replacing entirely.

A few solutions exist which use VoIP (Voice over Internet Protocol) to provide temporary connectivity. This may extend the life of your alarm system, but it isn’t ideal. VoIP is susceptible to frequency shifts and data errors — irritating on a phone call, but potentially disastrous during a break-in or fire.

Many legacy alarms simply do not have the required linking functionality, either to VoIP or the more preferable option, IP.

If your alarm system cannot integrate with IP, it’s time to consider an upgrade. That ensures your security is future-proofed.

Why sooner is better

As we mentioned previously, many businesses remain unaware of the full implications of the switch-off. However, that won’t last much longer.

As the date approaches, and publicity around the subject increases, there will undoubtedly be a rush to replace alarms which are about to become obsolete. If you leave it too late, there are likely to be problems with supply chains, lead times and the availability of engineers.

There is also the question of insurance. Should your cover be dependent on alarm systems and CCTV surveillance, you will want to avoid the risk of experiencing an alarm signalling failure and invalid insurance cover.

Will all alarm systems need replacing?

Not necessarily. Many modern alarms are already able to integrate with IP networks. If this is the case, all you may need is an engineer to switch it over.

If your alarm communicates via cellular signalling rather than phone lines, this will be unaffected and there will probably be no need to make changes.

For peace of mind, we recommend you speak to an expert. For reliable advice, please speak to one of the team members at Classic Services Group, or contact us here. We can assess your alarms and, if they need an upgrade or replacement, discuss the most cost-effective options. We’re here to help you make the right decision.

Get in touch here.