What is VoIP, digital voice, and all-IP?
In brief
- VoIP, digital voice, all-IP, SIP, and "internet calling" all describe the same idea: carrying voice calls over a broadband connection instead of the old analogue phone line.
- Providers use different brand names (BT Digital Voice, Sky Talk, Virgin Media Home Phone, TalkTalk Future Phone), but the underlying technology is the same.
- For the user, the main difference is that the phone plugs into the broadband router instead of the wall socket and the line stops working in a power cut without a backup.
- Call quality, dialling, and 999 access are the same as before as long as the router has power.
What does VoIP stand for?
VoIP stands for Voice over Internet Protocol. Instead of your voice travelling as an analogue signal over a copper phone line, it is broken into small packets of data and sent across an internet connection, then reassembled at the other end. The receiver hears a normal phone call.
VoIP is not new. Business telephony has been running on VoIP since the early 2000s. Consumer apps like Skype and WhatsApp Calling use VoIP. What is changing in the UK is that the public landline network itself is moving from the old analogue system to VoIP, so that every home phone eventually becomes a VoIP phone.
Why do I see so many different names for the same thing?
The same technology goes by different names depending on who is talking about it:
- VoIP: the generic technical term.
- Digital voice: the plain-English term Ofcom and most providers now use with customers.
- All-IP or IP voice: telecoms-industry shorthand for the whole PSTN replacement programme.
- SIP: a specific technical protocol used to set up VoIP calls. If you see "SIP trunk" that is a VoIP connection for a business phone system.
- BT Digital Voice, Sky Talk, Virgin Media Home Phone, TalkTalk Future Phone: provider brand names for the same underlying service.
In everyday conversation, if someone says their landline is on "digital voice" or "VoIP", treat the terms as interchangeable.
How VoIP differs from the old landline
For most people the difference is small but practical:
- Where the phone plugs in. Old: into a wall socket. New: into a phone port on the broadband router.
- Power. Old: the phone line carried a small current, so a basic corded phone worked in a power cut. New: the router needs mains electricity, so the phone stops working during a power cut unless you have a battery backup.
- Quality. Usually the same or slightly better. Occasionally, if broadband is congested, you may hear a tiny delay or slight distortion.
- Features. Digital voice can add features like call-blocking, visual voicemail, and spam filtering that the old line did not offer.
What stays the same: your phone number, how you dial, 999 access (while the router has power), most handsets, and your monthly cost.
Does VoIP need broadband?
Yes. You cannot have digital voice without an internet connection. Most homes already have one, so the change is invisible. For a small minority of households with no broadband, providers have to offer an alternative: either a basic broadband line used only for voice, or a mobile-based landline replacement. See our landline options if you have no broadband guide.
What about 999 on VoIP?
999 works on digital voice exactly as it did on the old landline, as long as the router has power. Providers are required under Ofcom's General Conditions to give customers at least one way to reach 999 during a power cut. That is usually a battery backup for the router or a pre-paired mobile handset. Full detail in emergency calls and 999.
Common questions about VoIP and digital voice
Is VoIP the same as digital voice?
Yes. "Digital voice" is the plain-English name for VoIP in the context of the UK landline switch. BT calls it Digital Voice, Sky calls it Sky Talk, TalkTalk calls it Future Phone. Same technology, different brand names.
Is VoIP safe and reliable?
For everyday calls, yes. Call quality is typically the same as the old landline. The main new risk is power cuts: without mains power, the router shuts down and calls stop. Mitigate by asking your provider for a battery backup or keeping a charged mobile phone as a backup.
Will VoIP affect call charges?
Not usually. Moving to digital voice does not by itself change your line rental or call charges. Your existing plan moves across with you.
Can I use VoIP without a landline?
Yes. Internet calling apps like Skype, WhatsApp, and Zoom are VoIP-based and do not need a landline. But the UK national phone network is itself moving to VoIP, which means every home landline is becoming a VoIP service whether you opt in or not.