Digital landlines in a power cut: calling 999

Most of us rarely think about how our home phone gets its power. With the old copper landline, you did not need to: the line carried its own electricity from the telephone exchange, so a simple corded phone usually kept working even when the lights went out. As landlines move to digital, that is changing. This guide explains what happens to a digital landline in a power cut, what support is available, and the simple steps that help you stay ready to call 999.

Why a digital landline needs power

A digital landline, sometimes called VoIP, carries calls over your broadband. With full fibre, your connection relies on two pieces of equipment in your home: the fibre box on the wall and your router. Both run on mains electricity. If the power goes off, they switch off, and so does any phone that connects through them.

Ofcom explains in its guidance on VoIP services that emergency calls over broadband may fail in a power cut or broadband outage, and that providers must make this clear to customers. This is not a fault with any one provider; it is how the technology works.

The old copper network is being retired, with Openreach lines due to move to digital by 31 January 2027, so this now affects most households whoever their provider is.

The free one hour solution

Some people rely on their landline more than others. Ofcom requires providers to offer customers who depend on their landline at least one solution, free of charge, that gives at least one hour of access to emergency services during a power cut.

You are likely to be someone who depends on your landline if, for example:

• you have no mobile phone;
• you cannot get a reliable mobile signal at home;
• you would find it hard to use a mobile phone in an emergency; or
• you have a telecare or personal alarm that uses your phone line or broadband.

The solution your provider offers might be a battery backup unit for your router, or a phone that works without mains power. It is designed to cover the minimum of one hour. Ask your provider exactly what they offer and how long it lasts with your equipment. If you think you qualify, please tell your provider; it may not know unless you say. Our extra help page explains how to tell us.

Battery backup for everyone else

Even if you do not depend on your landline, you might want your broadband and phone to keep running during a short power cut. A battery backup unit, sometimes called a UPS, sits between the wall socket and your equipment. When the mains supply stops, it takes over.

A few practical points to bear in mind:

• Power both boxes. The fibre box and the router both need power, so the backup must supply both.
• Running time varies. How long a unit lasts depends on its size and on how much power your equipment draws. Check the manufacturer's information.
• Batteries age. Backup batteries hold less charge over time, so check them now and then and replace them when advised.
• Cordless phones need power too. A cordless phone base station plugs into the mains. A corded phone plugged into the router or adapter is a better choice for a power cut.

Your mobile is your best backup

For most households, a mobile phone is the simplest way to call 999 during a power cut. You can call 999 or 112 from a mobile even without credit. To be ready:

• keep your mobile charged, especially during stormy weather;
• keep a charged power bank somewhere easy to find;
• check which rooms in your home have the best signal; and
• make sure everyone in the household knows how to unlock the phone and make an emergency call.

Keeping your 999 address right

When you call 999 from a landline, your provider passes your registered address to the emergency services. With a traditional line, that address was fixed to the copper wire. With a digital line, it is a record your provider holds, so it is important that it is correct.

Check your address with your provider when your digital line is set up. If you move home and take your phone service with you, tell your provider straight away so they can update it. Always tell the call handler where you are if you can, but an accurate registered address is a valuable safety net.

A simple power cut plan

1. Keep a torch and a charged power bank where you can find them in the dark.
2. Keep your mobile charged and know where the signal is best.
3. Tell your provider if anyone at your address depends on the landline, and ask about the free solution.
4. If you have a telecare alarm, ask the alarm provider what happens in a power cut.
5. Note the number for your electricity network operator. In Great Britain you can call 105 to report or get updates on a power cut.

How Cyber Fibre helps

Cyber Fibre provides full fibre broadband with one VoIP phone line that you can add, keeping your number if you wish. When you order, you can tick a box to tell us that someone relies on a landline or alarm, and we will call you before installation to talk through power cuts and the support we can offer. Our power cuts and 999 page sets out the essentials, and our call rates page explains how calls are charged.

Find out more

If you have questions about power cuts and your phone, we are happy to help. Check your address to see the full fibre packages available, or call our Sunderland team on 0191 543 3432.