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Message 1 of 12

Digital Voice Backup Battery

I have managed to delay my switch over to Digital Voice until I can be provided with a battery backup.  This is because my wife is vulnerable and in the event of a non medial emergency I need to contact neighbours for help. (I have no mobile signal so cannot use that medium).   We had a power cut yesterday due to storm Eunice and a number of neighbours visited me to use my analogue phone(!).  Some time ago I wired up a battery backup to the BT router for one of my neighbours who is in their 80s and at times needs help (BT supplied her with the battery backup device). When we had the power cut yesterday I phoned this neighbour to make sure their battery backup was working.  To my surprise her battery backup did not work in terms of her being able to make or receives calls - I had to use my analogue phone to call her daughter.  The battery backup did work in that the router was powered and lit up - but it was flashing purple.   As I wired this up I was intrigued and soon realised  that the reason this 'backup system' was never going to work is because the fibre/broadband terminal box that the router is wired to is itself mains powered.  So .... in the event of a power cut the router is powered by the backup battery, but has no broadband connectivity because the incoming terminal box is not powered.   Hmm....

I might be missing something here but the battery backup box is a simple device having a connection into the routers mains input - there is no way it can also power the terminal box.   There may be other models but this was the device sent to my neighbour and presumably BT were aware of the 'set-up'.  Are there other models of backup battery or have I got this all wrong?  (Power is restored today and I tested the router/terminal box in my own house.  Obviously when I powered down the terminal box the router started flashing purple because it lost its network connection.  So I cannot see how the backup backup can possibly work in terms of being able to make and receive calls when it only powers the router).

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Message 2 of 12

Re: Digital Voice Backup Battery

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Message 3 of 12

Re: Digital Voice Backup Battery

???????  Hopefully some help may be following

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Message 4 of 12

Re: Digital Voice Backup Battery

It depends on how the broadband is delivered, anything that requires power would need a backup unit.

If you have Fibre to the cabinet (FTTC) the broadband comes through the master socket, this means the battery backup unit (BBU) needs to keep the Smart Hub 2 powered.

If you have Fibre to the premises (FTTP) the broadband comes from the ONT, this means the battery backup unit (BBU) needs to keep the ONT and the Smart Hub 2 powered.

Any phones that need electricity would also need a backup, I would also advise contacting your energy provider, they willl prioritise vulnerable customers during a power cut.
Mobile networks also allow sharing when it comes to emergency calls to 999, you would only need a signal from 1 of the 4 mobile networks to make a 999 call, even if your mobile provider has no coverage.

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Message 5 of 12

Re: Digital Voice Backup Battery

I've been through this ring 999 loop before with my MP - thank you for your suggestion.  Looks like I'm going to have to contact my MP, Ofcom and BT CEO again - as on the surface it appears BT does not have a solution to forcing customers into vulnerable situations in the event of power cuts when making them switch to Digital Voice.  I will get a definitive statement from BT's CEO about ringing 999 for non medical help before going back again to my MP.  Thank you.

Message 6 of 12

Re: Digital Voice Backup Battery


Looks like I'm going to have to contact my MP, Ofcom and BT CEO again

Why ? You said BT have delayed your account, this is another customer you're discussing, if that person meets the criteria BT will provide a BBU free of charge which they already have.

This has already been discussed and agreed with the regulator Ofcom, you can read more at :




Message 7 of 12

Re: Digital Voice Backup Battery

Something like this will cover all your needs:


When I say 'all' I mean most eventualities.

I do think truly rural areas (a few in Scotland had no power for 8 days a few weeks back which is unacceptable) need to have some sort of backup for themselves (ie a generator) but also something supplied by councils/government maybe in a local shop like a satellite mobile telephone. 

I have a backup myself for my FTTP and if I lived in a rural place I'd also have a generator or two.

I wouldn't bother my MP it's up to all of us to do as much as possible for ourselves and if people really can't cope then century old technology (which needs electricty somewhere and intact cabling) copper line isn't going to provide for any miracles.

People need to be prepared and those who won't will just have to suck it up and those we can't will need statutory intervention by local authorities at some stage. Nothing new there.

Message 8 of 12

Re: Digital Voice Backup Battery

Thanks for this. I am in the same position as the person you were assisting ... I'm just getting fixed up with full fibre broadband and with a vulnerable adult that resides at home.

You've helpfully confirmed what I had gleaned thus far and I'm thinking of putting a small UPS device to support the surge protected short extension lead I already use to facilitate the OTM and SmartHub2 i.e. battery for the critical comms kit - if that works I can always add a larger capacity battery and/or similar devices to the hybrid connect & extension discs ..... see how the journey goes!

I do have good mobile signal at the property but if the cell tower is jammed up with calls or the vulnerable person didn't charge the phone - again 🙂 .... then the backup may well be needed at some point. It wouldn't be the first time.

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Message 9 of 12

Re: Digital Voice Backup Battery

I'm in a similar situation. I have just moved back to BT from NOW Broadband and am on Digital Voice.

I'm concerned about a power failure too, as although I have a mobile signal, the coverage is patchy and the mast is so congested sometimes, it is not reliable.

I contacted the Loyalty and Faults teams, but both are saying I would have to pay £85 for the BBU.

I live alone and have autism and so I would like the BBU for peace of mind and to avoid going into a meltdown should a power cut arise. I guess I probably don't fit the BT criteria of a vulnerable customer and I guess they see that theoretically, I should have a mobile signal at my location so would have to pay.


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Message 10 of 12

Re: Digital Voice Backup Battery

Some interesting info here on why BT paused the DV rollout and some potential new solutions like hybrid phones which switch to mobile networks during a power cut, I haven’t seen anything like this for sale yet though.