Will your phones work on a digital landline?

The old landline network, the Public Switched Telephone Network (PSTN), carries calls as analogue signals to your wall socket. A digital landline carries them over your broadband instead. Ofcom, the communications regulator, says you plug your phone into your broadband router rather than the wall socket, and you can keep your number. Openreach says traditional phone lines on its network need to move to digital by 31 January 2027; Ofcom says Virgin Media O2 and KCOM, which run their own networks, haven't yet set dates for theirs.

Openreach says you'll need a broadband connection, a router or adapter (supplied by your provider if needed) and your current handset. Ofcom says the provider should explain and arrange any new equipment. BT says any new kit arrives before switch-over day and there's no charge for Digital Voice, its name for the service. Vodafone sends an adapter for the router, plus a new router if yours is an older model. Virgin Media replaces Super Hub 1, 2 and 2ac models free.

The phone now depends on the router. BT says the hub must be switched on and connected to broadband, though Wi-Fi strength doesn't matter. Virgin Media says its home phone won't work if the Hub is off (it does in modem-only mode), and rebooting the Hub ends a call in progress.

Usually, yes. Openreach says most will, though some older phones may not be compatible and your provider can help you check. Virgin Media says you won't have to change your handset, and TalkTalk says no specialist Digital Voice handset is needed.

The exceptions are specific, and worth checking before switch day:

• Tone dialling (BT). BT says any tone-dialling phone can be used with Digital Voice, plugged into the hub or into a Digital Voice Adapter. Tone-dialling phones beep for each key; if yours is rotary or pulse-dial, ask your provider first.
• Older "bell-wire" phones (BT). BT says older bell-wire telephones aren't compatible with the BT Digital Voice Adapter. The EE Digital Voice Adapter is compatible, works with both BT and EE Smart Hubs, and BT says you can order one free online or by texting ADAPTER to 61998.
• Phones bought before 2015 (BT). BT says your own phone may not ring when connected to a Digital Voice Adapter if it was bought before 2015. BT supplies a free microfilter that fixes this: call 150 from a BT or EE mobile, or 0330 123 1105.
• BT-branded handsets on Hyperoptic. Hyperoptic says most standard handsets with an RJ11 port and plug (the small, square clip-in phone connector) are compatible, but BT-branded handsets won't work with its phone service.

If you're unsure, don't buy a new phone in advance: plug in what you have on switch day, test calls both ways, and replace it only if it fails. If you do buy one, BT's range includes an Emergency Hybrid Home Phone that switches to a built-in SIM for emergency calls in a power cut or broadband outage.

Cordless sets are the easiest to move. BT says plug the main base unit's phone cable into the hub's phone port, keep the base plugged into the mains, and the other cordless handsets work as usual. Virgin Media says the same: only the base station needs connecting to the Hub. If the router is somewhere awkward, BT says a Digital Voice Adapter lets you put the base in another room.

Two set-ups need more thought:

• Several separate base stations, each wired back to a phone socket. Virgin Media says this needs an engineer appointment. On BT, a base away from the hub connects through its own Digital Voice Adapter, within the limit of five adapters and Digital Voice handsets.
• Several corded phones in different rooms. BT says additional corded handsets, and normal (non-Digital Voice) phones beyond the one in the hub, each need a Digital Voice Adapter.

Some routers have a cordless base built in. Zen says the FRITZ!Box 7530 AX has a DECT base station (DECT is the wireless standard cordless home phones use) for up to six cordless handsets, and that its FRITZ!Fon C6 cordless phone works with Digital Voice. That only helps if Zen supplies a FRITZ!Box. Hyperoptic, by contrast, says to connect only one compatible handset at a time to its Hyperhub's phone port, so a cordless set with a single base is the natural fit there.

An extension socket is any phone socket beyond the main one where the line comes in. On most digital landline services they stop carrying calls. BT says extension sockets aren't supported on Digital Voice, Vodafone says extra telephone sockets won't work after the switch, and Community Fibre says old extension sockets won't carry its calls. Virgin Media says the old wall socket and anything connected to it will stop working. A phone on the landing will go quiet unless you act. Your options:

1. Go cordless. Plug one cordless base into the router and put extra handsets around the house. Vodafone suggests plugging all phones into the back of the router or using wireless phones that work with Digital Voice.
2. Use an adapter as a wireless extension (BT). BT's Digital Voice Adapter plugs into any mains socket, links to the hub without wires (you pair them with their WPS buttons) and works like an extension socket: plug your phone into the top and you should get the same dial tone as before.
3. Move the router. Virgin Media says that if the Hub and landline are in different rooms, it will arrange an engineer to move them closer together for free.
4. Ask about the wiring. BT says if using your extension wiring is essential, call 0330 123 4150 to talk through the options, and that adapters are available to replace extension sockets.

A BT exception. BT's help pages mention a service called Home Phone Standard, on which extension sockets and telecare should continue to work as normal. The same page warns that some devices can still show errors or stop working after that move, and recommends a test call to your telecare provider once it's active. The page doesn't say who gets it rather than Digital Voice, so ask BT which service you're moving to before changing any wiring.

A built-in answer machine sits inside your phone or cordless base and records messages there. Network voicemail, such as 1571, is run by your provider and keeps messages on its system.

• Built-in answer machines travel with the phone. Vodafone, whose own voicemail doesn't work with its Digital Voice, says you can still use voicemail on phones with built-in answer machines.
• Network voicemail depends on the provider. On BT Digital Voice an interrupted, different dial tone means a message is waiting; Digital Voice handset users press the voicemail button and all other phones dial 1571. Vodafone says its Digital Voice doesn't work with Vodafone voicemail, conference calls, call diversion or call management features such as anonymous caller rejection.

Some routers have an answering machine of their own. Zen says the FRITZ!Box 7530 AX has a built-in answering machine that stores messages and can send them to you by email. We haven't found provider guidance on standalone answering machines; if you use one, include it in your switch-day tests.

Call blockers. Virgin Media says to unplug a separate call-blocking machine from the phone socket and plug it into the Hub using the adaptor.

Ofcom tells customers to let their provider know before the change if they have a care alarm, security alarm or other device that uses the phone line. It says that if you mention a care alarm or telecare device in advance, the provider can help check whether it will work and pause the change until a safe solution is in place. For alarms, telecare and fax machines, GOV.UK says you might need to upgrade the device, check whether it needs its own battery and network back-up, or buy an adaptor; if unsure, contact the supplier. When buying new kit, check it works with VoIP (voice over internet, the technology digital landlines use) or can connect to mobile services such as 4G.

Text relay. Virgin Media says next-generation text relay on devices with their own SIM is unaffected, and that users of older text relay can move to next-generation text relay or the Relay UK app.

If anyone in the home uses a personal alarm, pendant or other health device that relies on the phone line, read our guide to telecare and personal alarms on a digital landline before anything else.

The old copper line carries a little power from the exchange, enough, GOV.UK says, to run some basic corded phones in a power cut. Digital landlines can't carry power, so phones and routers rely on your home's electricity. BT says you can't make calls, including to 999, from phones on the hub or an adapter during a power cut or broadband problem.

Hyperoptic says that with a battery back-up you need a corded phone plugged into the Hyperhub, as DECT cordless phones won't work in a power failure. TalkTalk offers a battery back-up lasting up to an hour to customers in areas with no mobile signal. Our guide to digital landlines in a power cut covers the options.

The points above, in the order you'll need them.

If you're changing provider anyway, weigh the phone set-up alongside price and speed. Some providers sell the home phone as an optional extra, as Community Fibre does with its Calls service. When you compare broadband and phone deals, check:

• Whether a home phone is included or an add-on.
• Which router comes with it, and whether it has a phone port or a built-in cordless base.
• Whether the provider supplies adapters for phones in other rooms.
• Which voicemail and calling features work on its digital service.

The comparison shows live packages for your postcode; check the phone details before you order. If you don't need calls, broadband-only deals are worth a look. And if you want to bring your existing number with you, read how to keep your landline number when switching first.