Short answer: Broadband and your home alarm after the switch-off only need careful checking if the alarm uses the old telephone network. Before changing service, ask your alarm company how it communicates and whether it needs a compatible digital connection, power backup or an equipment upgrade.
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- The old landline network, known as the PSTN, is due to close on 31 January 2027.
- An alarm that depends on a traditional phone line may need testing or changing before your broadband service changes.
- Do not cancel, move or switch broadband until the alarm company has confirmed its requirements.
- A broadband switch does not automatically mean your alarm will stop working, but compatibility is specific to the alarm and its signalling method.
A family moving into a house may reasonably focus on installation dates, Wi-Fi and monthly cost. But if the property has a monitored alarm, the connection behind it matters just as much. A new broadband service can be right for the household, while the existing alarm still needs a separate compatibility check before the change goes ahead.
What happens to a home alarm after the landline switch-off?
Answer: alarms that rely on the old phone network need to be checked before that network closes.
The Public Switched Telephone Network, or PSTN, is the older landline network that has carried traditional voice calls for decades. It is scheduled to close on 31 January 2027 (Openreach, 2027). That date matters if your alarm sends alerts through a conventional telephone line.
Some alarms use a different connection already, while others may rely on equipment connected to the landline socket. You cannot tell which applies simply by looking at the alarm keypad or by assuming that a working house phone means the alarm is ready. The alarm company should identify how the system sends signals and what it will need after the change.
Start with the landline switch-off checker if you are unsure what the wider change means for your household. It is sensible to make this check before choosing a new contract or arranging an installation date.
Does my alarm use the old telephone network?
Answer: only your alarm company can confirm the signalling method and whether your equipment is compatible.
Look for paperwork from installation, monitoring or servicing, but do not rely on old documents alone. Equipment may have been altered since it was fitted, and the relevant question is how it communicates now. Tell the company that your telephone service may be moving away from the old network and ask for a clear answer in writing.
Ask whether the alarm is connected to the landline, whether it can work with a digital voice service, and what happens if broadband or mains power is unavailable. If it needs replacement equipment, ask who supplies it, whether a visit is needed and whether testing is included.
This is also worth doing if you rent. The alarm may belong to the landlord, building manager or previous owner, but you should not assume someone else has checked it. Our guide to broadband for renters explains the separate permissions and setup questions that can arise when you change service at a rented home.
Will broadband keep my alarm working?
Answer: it may, but a broadband connection is not a substitute for confirmed alarm compatibility.
Many homes will receive voice services digitally rather than through the old telephone network. Digital voice means calls are carried using the broadband connection instead of a traditional copper telephone service. Whether an alarm can use that arrangement depends on its own equipment and the alarm company’s requirements.
There is another practical point. Digital services in the home can depend on both working broadband equipment and electricity. That is why you should ask specifically about power cuts, rather than assuming the new setup behaves exactly like the old one. If the alarm company recommends backup equipment or a different signalling arrangement, get the details before placing your broadband order.
Do not test an alarm by disconnecting cables yourself. You could trigger an alert or leave the property without the protection you expect. Arrange any testing through the company responsible for the alarm.
Which broadband setup is right for an alarm?
Answer: choose the connection available at your address, then make sure the alarm is designed for it.
Broadband technology affects installation and the equipment entering your home, but it does not by itself certify an alarm. Full fibre, also called FTTP, brings fibre directly to the property. Other homes may use a part-fibre connection or a cable network. Your alarm company needs the actual compatibility details, not just a broad label such as “fibre”.
| Home connection situation | What to check for the alarm | Best next step |
|---|---|---|
| Traditional landline currently in use | Whether the alarm depends on that line to send signals | Ask the alarm company for a switch-off assessment |
| Digital voice delivered through broadband | Whether the alarm equipment is compatible and what it needs during a power cut | Arrange testing before the service changes |
| Full fibre installation planned | Where new equipment will be fitted and whether the alarm needs altered wiring | Share the installation date with the alarm company |
| Moving home | Whether the alarm at the new address is active, owned by you and compatible | Check before committing to a moving date |
Check what is available at your address through our full fibre broadband deals page. Availability is address-specific, so it is better to check than to plan around a technology you may not be able to order.
What should I ask before switching broadband?
Answer: get the alarm requirement first, then match your broadband order and installation timing to it.
Ask the alarm company whether your current system requires a phone line, whether it works with digital voice, and whether it needs a site visit or replacement unit. Ask what you should do during an outage and whether there is any required testing after installation.
Then ask the broadband provider how the installation is expected to work at your address, including whether an engineer visit is needed and whether existing equipment will change. Do not present this as an emergency fault after the switch has completed. Raising it before ordering gives you more chance to schedule the work in the right order.
If you are moving, build the alarm check into the same plan as your service move. The moving home broadband guide can help you separate address availability, installation timing and contract choices before moving day.
How can I switch without disrupting my alarm?
Answer: confirm the alarm plan first, keep records, and let the new broadband provider manage the broadband switch.
For most residential broadband switches, One Touch Switch means you contact the new provider, which manages the switching process with the old provider. The process went live on 12 September 2024 and is run by TOTSCo (TOTSCo, 12 September 2024). It reduces the need to chase two providers, but it does not replace the separate conversation with your alarm company.
Avoid choosing a cease date that leaves the alarm without its required connection. Keep the written advice from the alarm company, your broadband order confirmation and any installation appointment together. If dates change, tell the alarm company promptly.
For the wider broadband process, see our guide on switching broadband and the details of One Touch Switch. The main principle is simple: let the broadband switch be managed through the normal process, while treating alarm compatibility as its own essential check.
What to do next
- Contact the company responsible for your alarm and ask how it communicates after the old telephone network closes. Request its answer and any recommended work in writing.
- Check installation timing, equipment changes and power-cut arrangements before you accept a broadband order or move date.
- Use a postcode check to see the broadband options available at your address, then choose a service that fits the confirmed alarm plan.
Frequently asked questions
Will my home alarm stop working when the PSTN closes?
Not necessarily. It depends on how the alarm communicates and whether its existing equipment is compatible with the replacement arrangement. The PSTN closes on 31 January 2027 (Openreach, 2027), so ask the alarm company to check your system rather than waiting for a problem to appear.
Can I switch broadband if I have a monitored alarm?
Yes, but check the alarm first. A broadband switch and an alarm service are separate arrangements, even where the alarm uses a phone connection. Confirm the required setup, testing process and timing with the alarm company before your new broadband service is installed.
Does full fibre affect my alarm?
Full fibre may change the equipment and wiring used for your home connection, but it does not automatically tell you whether an alarm will work. Give the alarm company the details of the planned installation and follow its advice on compatibility, power backup and any equipment changes.
Should I cancel my old broadband before switching?
Usually, no. Under One Touch Switch, you contact the new provider and it manages the switch with the old provider for most residential moves (TOTSCo, 12 September 2024). Do not make separate changes that could disrupt an alarm connection without checking the consequences first.
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A careful alarm check now can make your broadband change feel routine rather than risky. Keep the alarm company’s advice beside your broadband order, and schedule both around the same installation plan.