999 calls in a power cut

The UK is just starting on the "digital phone line" changeover (often referred to as "Digital Voice"). It's due to finish by the end of 2025. 

The changeover makes great sense from many angles, but it introduces one big challenge - how people can contact 999 emergency services if their electricity is off?

Click on the flowchart image to see it in detail, or read on for the explanation of why things are set to get a lot harder if you want to be able to call 999 if the power is off.

How often do people need to call 999 when their power is off?

The chance of needing to call 999 is higher when your power is off than at other times:

• You may need to report an emergency that caused your power to fail (eg a fire or flood that has tripped your home supply).

• People are more at risk when fumbling around when the power is off - fires from candles or lanterns, tripping up, or scalding themselves filling a hot water bottle, for example.

Can't people just use their mobiles for 999?

Already, most 999 calls come from mobile phones. But that doesn't mean that the mobile network is an adequate replacement for the ability to call from a pre-digital landline.

For those with a strong mobile signal

The majority of people, those who have a decent mobile signal at home, won't anticipate a problem with relying on their mobile for 999 calls if the power is off. 

Will that actually work in practice? It seems that nobody knows, as there is no requirement for mobile phone masts to have backup power. So if the power cut is over a wide area, all the available masts may have lost their grid power. What proportion of UK would still be able to make a 999 call from their mobile 10 minutes into a widespread outage? Ofcom doesn't know. So it's quite possible that those without any obvious problems are still facing a new risk: if your power is off and your mobile can't get you through to 999, you won't be able to fall back on placing a voice call through your digital landline.

For those who can reach 999 only via a different network

Of those who don't have a good mobile signal, some will be able to reach 999 via a different network - there is a special system for this. But what hasn't been explained widely is that calls made in this way can't be returned. So if an ambulance crew can't find your house, their control room can't call you back to sort out the problem. Ofcom couldn't initially confirm whether this was true. And when eventually they did concede this, they gave no indication that they considered this a problem that needed fixing given the greater reliance on mobile calls to 999 once we have moved to digital landlines.

For those who don't have a usage mobile signal on any network

This group is facing the biggest challenge. If your only way of reaching 999 in a power cut is through a non-digital landline, you are going to be in trouble when that line is changed to digital.

Non-digital landlines keep working for many hours during a power cut: there are batteries in the exchange to keep things going, and enough power down the line to run a "corded" handset at your end.

But digital landlines don't send power down the line - they only work while there is electricity at your end to run the router (or other device) that will let you make voice calls. They stop the moment your power fails.

Ofcom realise this is a problem. They have issued "guidelines" that specify that Communications Providers must offer a "solution" to the problem - without charge. For those without a usable mobile signal, that solution has to be a Battery Backup unit.

But there are some major problems with this:

• Ofcom has decided that it will be OK if the backup unit only lasts for the first hour of an outage. If you have an emergency two hours into a power cut, then even if you haven't made any calls or made any use of the internet, the Battery Backup Unit will have run out of power and you won't be able to make a call. Ofcom's reasoning is that most power cuts lasted for less than an hour - but a third of them lasted longer. And remember that in autumn 2022, we were being told to prepare for possible rota power cuts, and that these would last for three hours at a time.

• Ofcom aren't clear on who is meant to provide the Battery Backup Units. If you are a customer of Plusnet (who won't be providing a Voice service in the digital era), then you will end up with different companies providing the Broadband and Voice elements of your service. Ofcom aren't clear on which of them should be providing a Battery Backup Unit. And because the units are expensive (the only ones I could find cost £40 and £84.99 retail), the result is that virtually nobody is actually doing what Ofcom has specified in their guidelines.

• BT (who, as provider of both Broadband and digital voice services, can't avoid responsibility for offering Battery Backup Units) don't seem to have anything to say about BBUs. Instead, their current strategy seems to be to avoid converting anyone away from PSTN if they would qualify for a BBU. They say that they are not "proactively switching" anyone in the following categories

• Customers with a healthcare pendant 

• Customers who are over 70  [is that anyone in the household over 70, or does it need to be everyone?]

• Customers who only use landlines 

• Customers with "insufficient mobile coverage" [if I have signal in one room but nowhere else, do I qualify as "no mobile signal"? A signal on my "own" network, or on any network?] 

• Customers who have disclosed any additional needs 

Crucially, they say that BT will hold off (for now) only "where it has this information available".  I have asked BT's Press Office (twice) how customers make sure that BT has the relevant information, and they ducked the question. 

• Ofcom appear to be trying very hard not to notice that nobody is doing what they have divined. They claim to have checked and found no problems, but a few hours' research demonstrated to me that only one Broadband supplier (FTTP provider Hyperoptic) is offering Battery Backup Units for those without a usable mobile signal. I also contacted four digital voice (VOIP) providers who are offering residential services in the UK - none have an intention of providing Battery Backup Units.

The move to digital landlines is a major change, happening now. The increased risk of not being able to reach the emergency services is non-trivial. But the issue is getting very little press coverage (and no visible advertising campaign from Ofcom or from telecoms companies). We are sleepwalking towards serious danger.

If you want chapter and verse on the issue, and Ofcom's inaction, details (including sources) are in this PDF.

John Geddes
Winster, Derbyshire

November 2023