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Alarm technologies change with the passage of time and bring loads of new capabilities with new infrastructural, hardware, and software integration. However, with these new changes, what happens to old alarm systems?
One of the biggest changes happening in the security world is the adoption of digital services over the now-legacy Public Switched Telephone Network, or PSTN service.
PSTN is essentially a protocol that your alarm systems use to communicate to the monitoring system. It uses a telephone line to communicate alarm events and alert the monitoring system or Alarm Receiving Centre (ARC).
With PSTN switching off in early 2027 (31st January), many legacy hardware users are worried about the current status of their alarm systems.
Are the old alarms obsolete? Will they cease to work after the official switch-off date?
Read below to learn more about these new changes, what they mean for your alarm system, and a quick checklist for the impending PSTN switch-off:
ALARM MONITORING
- Confirm how your alarm currently signals (landline/PSTN, 2G/3G, 4G/5G, or broadband/IP).
- Check whether it is connected to an Alarm Receiving Centre and that signals are still being received.
- Ask your insurer what signalling grade or path they require (single-path or dual-path).
- Book an assessment if the panel or communicator is older, incompatible, or unconfirmed.
- Test the system after any migration and keep written confirmation from your installer or ARC.
To understand what the PSTN switch-off means, we need to go through a quick refresher about how these alarm systems work.
Alarm systems rely on on-board sensors and a communication protocol to detect and send out notifications of an alert or security event.
When an intruder is detected by the on-board sensor, the alarm uses the PSTN service to send out the signal to the ARC using a telephone line. This signal is received by the ARC, which can then take appropriate action.
The best alarm systems typically use Grade 4 alarm signalling services that allow the alarm to use two secure signalling paths to communicate with the Alarm Receiving Centre. It ensures that signals sent from the security systems are never compromised since it provides double protection against risks of failed alarm signals.
However, the PSTN network is being officially phased out. Why?
Well, because the PSTN network is now an outdated infrastructure and it is becoming increasingly expensive and difficult to maintain the network at current demand.
The PSTN was designed decades ago, with much of the underlying exchange equipment dating from the 1980s and 1990s!
Apart from the spare parts becoming harder to obtain and the decline in specialist engineering expertise, the network is simply becoming more difficult to maintain reliably, and reliability is key in security.
This is why the UK is moving to an all-IP or digital network, where voice calls and other communications are carried as digital data over broadband or fibre rather than through the old dedicated telephone network.
This is how the pathway of the alarm signal has changed from the PSTN to the new digital service:
PSTN network:
Telephone → copper line → PSTN exchange → telephone network
Digital/All-IP network:
Telephone → broadband/fibre → IP network
There are fewer “middlemen” technologies involved, which increases the reliability, speed, and security of the signal.
PSTN is expected to be switched off by 31st January 2027 with customers being migrated to digital, IP-based services.
This change, although natural in the technological evolution, is causing a lot of people with alarm systems to become confused.
Does this change affect your alarm system?
The good news is that the PSTN switch-off will not automatically mean that you will have to replace your alarm system. In most cases, the alarm system itself can remain in place while its communication equipment is upgraded.
THE PSTN SWITCH-OFF IS NIGH
- Confirm how your alarm currently signals (landline/PSTN, 2G/3G, 4G/5G, or broadband/IP).
- Check whether it is connected to an Alarm Receiving Centre and that signals are still being received.
- Ask your insurer what signalling grade or path they require (single-path or dual-path).
- Book an assessment if the panel or communicator is older, incompatible, or unconfirmed.
- Test the system after any migration and keep written confirmation from your installer or ARC.
How the PSTN switch-off affects your alarm system depends on how your alarm communicates with an alarm receiving centre, monitoring service, mobile phone, or other external system.
Most older alarm systems may use a conventional telephone line and a specifically built-in dialler to transmit alarm signals.
If this alarm system relies directly on the now legacy PSTN network, then it may no longer be able to communicate correctly after the switch-off date.
The good news is that most alarm systems, especially the ones made after 2010, may have alternative signal routing technologies built in.
These systems communicate using a modern IP, 4G, or another compatible communication method and may not be affected by the PSTN switch-off entirely.
We highly recommend that you call your security installation company or contact Calder Security to learn more about the specifications of your alarm system and whether your system will have to be replaced.
If you want to know the compatibility of your alarm system ASAP, then follow our guide below!
PSTN Switch-Off Guide and Troubleshooting 2026-2027
Here’s a guide to help you figure out if the PSTN network will affect your alarm system.
Start by identifying how your alarm sends signals.
Check whether the alarm uses a telephone line
The easiest way to detect if your alarm system will be affected by the PSTN change is to check whether the alarm uses a telephone line.
If your alarm panel has a traditional telephone connection or a built-in telephone dialler, it may need checking before your landline is migrated to a digital service.
Does this mean that your system will be replaced? Not exactly! As mentioned above, some systems can continue to operate through compatible digital services, while others may require an alternative communicator.
You can check the specifications of your alarm system by going to the manufacturer’s website and searching your system by its model or serial number.
If the alarm supports dialler/PSTN and IP technologies, then you may not need to upgrade your system at all.
Check for a GSM or mobile communicator
Another easy way to check your system is to look for a SIM card. Some burglar alarms use a SIM rather than a traditional telephone line.
These systems are designed to be future-proof since the SIM allows the system to connect via 4G; however, you will still need to check the mobile technology being used.
Keep in mind that 3G networks have already been switched off across the UK, while 2G networks are scheduled for retirement later in the decade.
If the alarm system uses a SIM and is designed for a 2G or 3G network, then you may need to replace the alarm, even if your home’s landline has nothing to do with the alarm.
Check whether the system uses IP or 4G
Newer alarm systems are designed to use IP-based connections or 4G mobile networks to transmit signals. These signals use digital means to transmit data, which means that they are fully compatible and will remain unaffected after the PSTN switch-off.
If your system uses IP-based technologies or 4G, then the PSTN retirement may not require an upgrade. A professional security company like Calder Security should confirm that the specific communicator, SIM arrangement, and monitoring service remain supported.
2026–27 Burglar Alarm Compatibility Checklist
Here is a quick checklist to help you stay on top of the eventual switch-off in early 2027:
Check the alarm panel
Begin by identifying the make and model of the alarm system. Then find out when the alarm system was installed on your property.
You will need to check whether it has a built-in telephone dialler by looking through the specifications or by going through the details on the back of the primary alarm. You can also identify this by checking the housing of the alarm to see if it supports an external communicator or a place for the SIM card.
Check the communication method
Once you have identified the alarm and its hardware specifications, you will need to figure out whether the alarm system uses PSTN or IP services.
Keep in mind that most alarm systems made after the 2010s will have dual connectivity features where they can fall back on alternative communication protocols. This can be in the form of IP services.
However, as we mentioned earlier, having IP services is not enough because the alarm needs to support 4G services.
Keep in mind that 3G services are phased out in the UK, with 2G to follow suit later in the decade. This means that your alarm system must either use 4G or IP/broadband protocols to communicate to the monitoring centre.
Check the monitoring service
If your alarm is being professionally monitored, then you can simply call the ARC and talk to a representative to learn more about how your alarm system transmits signals.
Monitoring providers are already reacting to these technological shifts and upgrading their systems, so chances are that you will not need to do anything at your end if the hardware is supported.
The ARC should not only support the new all-IP mantra going forward, but they must also seamlessly migrate all alarm systems connected to the service to digital channels automatically.
Test the system
When you are sure about the compatibility of your alarm system, we recommend that you give it a go and test it.
Testing it would require you to arm the alarm, trigger it, and monitor what happens next.
If everything is in order, the alarm system will successfully transmit the alarm signal to the ARC, and they will contact you for confirmation.
However, if the system fails to send the alarm, then you will need to call in the experts to diagnose the issue.
DO YOU NEED TO PANIC BECAUSE OF THE PSTN SWITCH-OFF?
- Confirm how your alarm currently signals (landline/PSTN, 2G/3G, 4G/5G, or broadband/IP).
- Check whether it is connected to an Alarm Receiving Centre and that signals are still being received.
- Ask your insurer what signalling grade or path they require (single-path or dual-path).
- Book an assessment if the panel or communicator is older, incompatible, or unconfirmed.
- Test the system after any migration and keep written confirmation from your installer or ARC.
One of the most common mistakes people make with alarm systems is that they assume that the alarm system will continue to work because it has just been serviced and is properly maintained.
Keep in mind that maintenance, while extremely important, will have no impact on the alarm signalling protocols of the system after the PSTN switch-off date.
With an incompatible alarm system, your alarm will appear to still function locally, but its external communication protocol will likely fail, making the alarm almost useless.
This is especially true for monitored alarm systems that send out signals externally. If an alarm cannot communicate with the monitoring centre, the property may no longer receive the level of monitored protection that you expect.
HELP, MY ALARM SYSTEM IS INCOMPATIBLE
- Confirm how your alarm currently signals (landline/PSTN, 2G/3G, 4G/5G, or broadband/IP).
- Check whether it is connected to an Alarm Receiving Centre and that signals are still being received.
- Ask your insurer what signalling grade or path they require (single-path or dual-path).
- Book an assessment if the panel or communicator is older, incompatible, or unconfirmed.
- Test the system after any migration and keep written confirmation from your installer or ARC.
If you have confirmed the incompatibility of your system, then there are two ways to go about it.
First, you may not need to replace the entire system at all. Depending on the system, an installer may be able to replace or upgrade the communications module on the system.
This method allows you to only swap out the old module with a new one, which will allow you to retain the existing control panel, calibration, detectors, external siren, and other components.
This is the best-case scenario and is highly likely for most alarm systems made after the 2010s.
If the system is indeed legacy and is entirely incompatible, then you will need to go the replacement route and reinstall the system.
However, there is a silver lining to replacing old systems. Most systems made before the 2010s have security gaps and older technologies that make them less effective at detecting threats. Also, due to the age of the system and sensors themselves, it may be a good idea to invest in a new system either way.
Not only will this allow you to future-proof yourself for the coming decades, but it will also ensure better, effective, and more reliable security for your property going forward.
Here are all the possible solutions for a compatible alarm system:
Upgrading an old telephone dialler,
Installing a 4G communicator,
Moving from an older mobile technology to a supported network,
Installing an IP communicator,
Introducing dual-path communication for greater resilience.
The correct solution depends on the alarm’s make, model, age, and existing communication equipment.
BOOK A BURGLAR ALARM COMPATIBILITY CHECK
- Confirm how your alarm currently signals (landline/PSTN, 2G/3G, 4G/5G, or broadband/IP).
- Check whether it is connected to an Alarm Receiving Centre and that signals are still being received.
- Ask your insurer what signalling grade or path they require (single-path or dual-path).
- Book an assessment if the panel or communicator is older, incompatible, or unconfirmed.
- Test the system after any migration and keep written confirmation from your installer or ARC.
Did you know: With the PSTN switch-off, you will need to externally power the alarm system to ensure that it sends out an alarm signal. Unlike the PSTN protocol which provides power through the telephone line, an all IP-based system will need you to always remain connected to the broadband to send the signal.
This is one of the few considerations that you will need to consider during the migration. Luckily, you do not need to worry!
At Calder Security, we take your security and changes in protocols seriously. We have been monitoring the changes ever since they were announced and are well-equipped to inspect your current system to ensure that everything is okay.
If you are unsure how your burglar alarm communicates, don’t wait until your telephone service changes in early 2027. Book a consultation today!
A security professional can inspect the alarm panel and communicator, identify the technology being used, assess the infrastructure, and determine whether an upgrade is required.
Not sure whether your alarm will still signal after the PSTN switch-off? Contact us here or call us on 0800 612 9799 for a free assessment.
WHY CHOOSE CALDER SECURITY FOR YOUR ALARM MONITORING NEEDS?
- Confirm how your alarm currently signals (landline/PSTN, 2G/3G, 4G/5G, or broadband/IP).
- Check whether it is connected to an Alarm Receiving Centre and that signals are still being received.
- Ask your insurer what signalling grade or path they require (single-path or dual-path).
- Book an assessment if the panel or communicator is older, incompatible, or unconfirmed.
- Test the system after any migration and keep written confirmation from your installer or ARC.
We are Yorkshire’s leading independent security company, and you can rely on us for all your alarm monitoring and migration needs.
Our alarm monitoring services work seamlessly with IP signalling services and offer you round-the-clock, uninterrupted monitoring of your property.
All our alarms are installed according to the British and European standards for alarm installation and monitoring. We are SSAIB-approved installers and have highly experienced security specialists who can advise on the best monitoring solution for you.
Our Alarm Receiving Centre (ARC) works 24/7 to ensure you receive the maximum level of security and peace of mind, even when you are away from your property.
We offer fast repair services if our monitoring detects any faults in the system, guaranteeing continuous safety and security.
We also offer installation, maintenance, monitoring, as well as repair services for all kinds of security systems for both your home and business. Regardless of how big or small your property is, we bet that we have the ideal security system for you!
Related reading: BT Redcare closure guide · Single-path vs dual-path signalling · Monitored alarms without a landline · Police response for burglar alarms · Burglar alarm services
Contact us here or call us at 0800 612 9799 to talk to our experts for more information on the PSTN switch-off and how it will affect your burglar alarm.
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