- Openreach plans to retire the analogue Public Switched Telephone Network (PSTN) and complete the migration to all-IP telephony in 2027.
- Digital Voice carries calls as data over a broadband connection rather than over a dedicated copper voice circuit.
- Ofcom requires providers to offer at least one solution that lets vulnerable customers contact emergency services for a minimum of one hour during a power cut.
- A handset plugs into the broadband router rather than into a wall master socket once Digital Voice is active.
- Existing telephone numbers are normally retained when a line moves from PSTN to Digital Voice.
Digital Voice is BT's IP-based home phone service that replaces the analogue PSTN. The handset plugs into the broadband router, the number is kept, and most customers are moved automatically as the network switches off by 2027.
Last reviewed: June 2026
What Digital Voice Is
For more than a century, telephone calls in the United Kingdom travelled over a dedicated analogue circuit known as the Public Switched Telephone Network, or PSTN. That network is ageing, increasingly difficult to maintain and reliant on equipment that is no longer manufactured. Openreach, the company that runs the physical access network used by BT and most other providers, is therefore retiring the analogue voice platform and moving every line to internet protocol delivery, a programme commonly described as the all-IP migration. BT's consumer brand for the new service is Digital Voice.
Digital Voice is not a new telephone number, a new tariff or a different company. It is a different method of carrying the same call. Instead of a continuous analogue signal running down a copper pair to the local exchange, the voice is converted into digital data and sent across the broadband connection. To the person making or receiving the call the experience is intended to be familiar: a dial tone, a number, a ring and a conversation. What changes is the technology underneath and, importantly, where the telephone plugs in.
How Digital Voice Differs Technically From the PSTN
On the analogue PSTN, the master socket on the wall provided line power and a permanent voice path that worked independently of any other service in the home. A handset could be plugged straight into that socket and would function even if the household had no broadband at all. The line carried its own low-voltage feed from the exchange, which is why a traditional phone kept working during a domestic power cut.
Digital Voice works differently. The voice signal is digitised and packaged into data packets that travel over the broadband line alongside web browsing, streaming and everything else. The telephone no longer connects to the wall master socket: it plugs into a dedicated telephone port on the broadband router, or connects to the router using a digital handset. Because the call now depends on the broadband service and on the router being powered, the resilience characteristics are different from the old copper line, which is the single most important practical change for households to understand.
What Equipment Is Compatible
Most existing corded and cordless telephones continue to work with Digital Voice. The handset itself does not need to be intelligent: it simply plugs into the telephone socket on a compatible router rather than into the wall. Where a household has extension sockets wired around the property from the old master socket, those internal extensions are not automatically fed by the router, so a cordless phone with multiple handsets, or a small adaptor, is often used to provide coverage in more than one room.
Some specialist equipment needs closer attention. Personal alarms and telecare pendants, fax machines, certain monitored burglar alarms, payment terminals and lift emergency telephones were designed for an analogue line and may not behave correctly over an IP service. Devices that rely on standards such as BS EN 81-28 for lift alarm communication should be checked with the equipment supplier before a line is migrated. Where a household relies on a monitored personal alarm, it is sensible to confirm compatibility with the alarm provider rather than assume the device will carry over unchanged.
The Power Resilience Issue
Because Digital Voice depends on the router, a Digital Voice line will not work during a power cut unless a backup power source is in place. This is the headline difference from the analogue line and the reason Ofcom has set out protections for at-risk customers. Ofcom expects providers to identify customers who depend on their landline, for example because they have no mobile coverage or rely on a telecare alarm, and to offer a solution that allows them to call emergency services for at least one hour in the event of a power failure.
In practice this protection usually takes the form of a battery backup unit that keeps the router and phone running for a period, or an alternative such as a mobile-based device, where the provider judges it appropriate. Households that do not fall into the vulnerable category are still encouraged to keep a charged mobile telephone available as a fallback. Anyone who is uncertain whether they qualify for additional support should raise it directly with their provider, because the obligation to offer a resilience solution is triggered by the customer's circumstances.
Who Gets Digital Voice First and the Comparison Table
The migration is being run region by region rather than all at once. Areas where the analogue network is closest to switch-off, and customers who are placing a new order or moving home, tend to be moved earlier. Customers with additional needs are handled with extra care and may be contacted separately so that resilience and telecare questions can be resolved before the line changes. The all-IP programme is scheduled to complete in 2027, so every remaining analogue line will move before then.
The table below sets out the core practical differences between the analogue PSTN and Digital Voice so that the change is easy to see at a glance.
| Feature | Analogue PSTN | Openreach Digital Voice |
|---|---|---|
| Call carriage | Analogue signal over copper pair | Digital data packets over broadband |
| Where the phone plugs in | Wall master socket | Telephone port on the router |
| Power during a power cut | Line powered from the exchange | Needs router power or battery backup |
| Telephone number | Existing number | Existing number normally retained |
| Network status | Being retired | All-IP migration completing in 2027 |
What You Need to Do
For most households the move is straightforward and largely handled by the provider. The first step is to make sure the provider holds correct contact details so any migration notice is received. The second is to take an inventory of anything connected to the existing line beyond the telephone: a personal alarm, a care-line pendant, an alarm system or a monitored device. Anyone who relies on such equipment, who has no mobile signal at home, or who has a household member who depends on the landline, should tell their provider so that an appropriate power resilience solution can be arranged.
When the line is migrated, the practical change at home is usually limited to moving the telephone cable from the wall socket to the router. The number stays the same and there is normally no need to learn a new dialling pattern. Keeping a charged mobile to hand remains a sensible precaution for everyone, given that the line now depends on mains power.
Frequently Asked Questions
What is BT Digital Voice?
BT Digital Voice is BT's name for its home phone service that carries calls over the broadband connection using internet protocol instead of the analogue PSTN. It is part of the wider Openreach all-IP migration that retires the copper voice network. The handset plugs into the router rather than the wall socket.
Will I get Digital Voice automatically?
Most customers are moved to Digital Voice as part of the planned migration rather than having to request it. The change is rolled out region by region, and new orders and house moves are often migrated first. Customers with additional needs may be contacted separately so resilience and telecare matters can be settled before the switch.
What equipment do I need for Digital Voice?
An existing corded or cordless telephone usually works, plugged into the telephone port on a compatible broadband router. A cordless phone with multiple handsets can provide coverage in several rooms because internal extension sockets are not automatically fed. Specialist devices such as personal alarms should be checked for compatibility with their supplier.
Does Digital Voice work in a power cut?
A Digital Voice line stops working in a power cut unless a backup power source keeps the router and phone running. Ofcom expects providers to offer at-risk customers a solution that allows at least one hour of access to emergency services during a power failure. Keeping a charged mobile available is a sensible fallback for everyone.
What do I need to do to switch to Digital Voice?
Make sure the provider has correct contact details, then list anything connected to the line beyond the phone, such as alarms or telecare. Tell the provider about any vulnerability or lack of mobile signal so resilience support can be arranged. When migrated, the main task is moving the phone cable from the wall socket to the router.
