BT Digital Voice

Posted: 23rd May 2021

If you are a BT customer, and have recently been converted to fibre broadband, then BT may also have offered to switch your landline to its new home phone service, known as Digital Voice. This is BT’s next generation landline telephony system, which uses Voice over Internet Protocol (VoIP) technology, instead of the traditional copper wired network, some of which has been around for 100 years or more. BT officially launched Digital Voice in February this year, although some customers had it installed and working before then. At the moment, if your broadband is to be upgraded to full fibre, then BT may or may not offer you the option to transfer to the new service: its plan is to convert the whole country by the end of 2025, so it’s definitely coming to everyone sooner or later. At the moment the rollout seems to be only to randomly selected customers. Some customers have reported that they have been offered the new service only if they change their phone number, whereas others have had it installed without such a change.

If you are upgraded to the new service, BT will provide one new advanced  handset (branded ‘Advanced Digital Phone’) or two new standard handsets (branded ‘Essential Digital Phone’) free of charge, which are designed to take advantage of the new service features. However, BT are not always forthcoming that new handsets are available free of charge, so if you have been or are about to be switched to Digital Voice, then don’t forget to ask about the availability of the free handset(s).
These handsets connect wirelessly to the new Smart Hub 2, using DECT: the Smart Hub is broadcasting both a WiFi and a DECT radio signal for this purpose. You can continue to use your old handsets if you so wish, by plugging one into the phone socket on the back of the Smart Hub 2, but your existing wall-mounted phone sockets will be de-commissioned; and the old phones will not be able to take advantage of many of the service’s new features.

The advantages of the new service include HD-quality calls (although I would have thought that it would be difficult to notice this until the whole network has been converted); the ability to have two lines on the same number (you can make or answer a call even if a call is already in progress on a different handset); and various free features which have previously required payment, such as voicemail and call-divert.

The main disadvantage of the new service is that, in the event of a power cut, your landline will not work. This is because Digital Voice relies on both the Openreach fibre modem (also known as the Optical Network Terminal or ONT - the white box inside your property to which the incoming fibre cable is connected), and BT’s Smart Hub 2 being powered on in order to connect to the network. In other words, you can no longer plug an old-style cabled phone into a wall socket and expect it to work during a power cut: your old wall sockets are de-commissioned, and the one on the back of the BT Smart Hub 2 will not work without power.

For most people, this news may not be significant - after all, only last month a new survey by market research company Opinium revealed that the humble telephone landline is in terminal decline, with 26% percent of people who have one not even bothering to connect a handset. But for those of us living in remote rural areas, where a mobile phone signal is weak or non-existent, and winter power cuts not infrequent, the landline telephone is still a regularly used and sometimes lifesaving necessity. The advent of BT’s Digital Voice is therefore not all good news for those who still very much rely on their landline, especially in the event of an emergency. It appears to be a major step backwards that BT are replacing a well proven telephony system that works in the event of a power cut with a new ‘improved’ version that doesn’t.

There are some workarounds for this inherent problem. Under OfCom guidelines, your telecoms provider is obliged to ensure that you are not left without a means of contacting the emergency services during a power cut, for a period of at least 1 hour. This means that if you do not have a mobile phone, or are in an area where there is no mobile phone signal indoors, then BT are obliged to supply two battery backup units (BBUs) to power both your fibre modem and Smart Hub 2, so that the new service will work during a power outage for at least one hour. The BT sales team should advise you of this fact when you sign up for Digital Voice, but they sometimes fail to do so (they didn’t inform us). If you have had the service installed already, and were not aware of this, then you can phone BT, ask to talk to the Broadband Faults and Complaints team, and they will send you a pair of battery backup units free of charge. However, one further problem is that upon enquiring with BT, I learnt that these BBUs are currently out of stock, and will not be available until at least next month. If you wanted to buy this equipment yourself from the BT shop (when available), the cost would be approximately £170, but cheaper alternatives are available from well-known online retailers (and, to the best of my knowledge, probably in stock).

BT however don’t make it easy to find this solution. If you enter ‘battery backup unit’ into the search box on the BT shop website, it will come back saying ‘No Results Found’. If you then send an email to the BT shop, enquiring as to the existence and availability of a battery backup unit (as I did), you will receive a reply saying, bizarrely: 'we do not provide this but it may be best to contact BT who will advise where you can get them' and 'Unfortunately we don’t deal with BT services or have any system integration with them'. Very strange, I thought they were the BT shop. Anyway, if you want to pay for one, it is possible to locate the required battery backup unit in the online BT shop by using the direct link at the end of this article.

As mentioned previously, BT plan to roll out the new Digital Voice service to all customers by the end of 2025, so it is coming to you, whether you like the sound of it or not. When you are scheduled to receive it, and if you are not one of the 26% of customers who never use their landline, then remember to do the following:
  • Ask BT which new free handset you will be receiving - remember, you can have 1 advanced, or 2 standard;
  • If you wish to maintain landline connectivity during power cuts, and don’t own a mobile phone, or have no mobile signal within your home, then insist that BT provide you with 2 battery backup units for the ONT and Smart Hub 2, as per OfCom guidelines.

Useful links:

Independent review of Digital Voice:

BT Digital Voice FAQs:

BT shop - battery backup unit for BT Digital Voice:

Alternative BBU from Amazon:

OfCom Guidance: Protecting access to emergency organisations when there is a power cut at the customer’s premises: (this is a lengthy document but the important part is on page 44)
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