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Guide · NBN landline and VoIP

Moving to the NBN? Your landline now runs over the internet

Moving to the NBN changes your home phone more than most people expect. Your landline now runs over the internet: it is an internet service that happens to make calls, not a line on its own wires. Most of the time that is fine. The exceptions, and there are a few that matter, are worth sorting before the switch, not after.

Last reviewed: 21 July 2026 · by Alien IT Solutions

Your landline is now VoIP

The old copper phone line ran on its own wires and carried its own power from the exchange, which is why the phone still worked in a blackout. The NBN replaces that.

Your home phone now runs as VoIP, Voice over IP: the call is turned into internet data and sent over your NBN connection, the same pipe as your web browsing and streaming. For everyday calls you will not notice the difference. What changes is how the phone connects, and what happens when the power or the internet goes out.

How you will actually plug the phone in

This is the part that catches people, because it depends on your provider and connection type.

  • Into the NBN box's phone port. Some providers let you plug a normal handset straight into the phone port, often labelled UNI-V or Phone 1, on the NBN connection box. Tidy, with no extra gear, but only if your provider supports it, and not every connection type has that port.
  • Into a VoIP adapter or your router. Other providers hand you a modem or router with a phone socket on the back, or a small VoIP adapter, an ATA. Your handset plugs into that, not the NBN box.
  • As an app. Some VoIP plans are app-only, or app plus handset: you make and take calls through an app on your phone or computer, with no physical handset needed.

Do not assume. Ask your provider exactly where the handset plugs in before the connection date, so you are not standing there with a dead phone on day one.

You can usually keep your number

You do not have to give up the number you have had for twenty years. Ask your new provider to port, that is, transfer, your existing number across when you set up the service. Two things matter:

  1. Start the port with the new provider, and do not cancel the old service first. If you cancel the old line before the number transfers, the number can be lost for good.
  2. Porting takes time. It can be same-day or take a few weeks depending on the number and the providers involved. Line it up before you need it.

Handset or app, pick what suits

  • A VoIP handset, a normal-looking cordless or desk phone plugged into the phone port or adapter, is best if you want it to feel exactly like the old phone: pick it up, dial, done. Good for anyone who does not want to learn anything new.
  • A phone app on your mobile or computer suits you if you travel, work from different spots, or want calls to follow you, but it depends on your mobile or data working, and it is a change of habit.

Plenty of households keep a physical handset as the house phone and treat the app as a bonus.

The big one: no power, no phone

This is the difference that actually matters, and it catches people out. When the power goes out, your NBN phone goes out with it. The NBN box and your router both run on mains power. No power to them means no internet, which means no phone, no 000, nothing. The old copper line kept working in a blackout; VoIP does not.

That is a genuine safety issue for:

  • Anyone with a medical alarm or personal-alert pendant that dials out over the phone line.
  • Security or fire alarms that report over a phone line.
  • Households where the landline is the main way to call for help, or where mobile coverage is poor.

What to do about it:

  1. Fit a UPS or battery backup for the NBN box and router so the phone keeps working for a while during an outage. Ask your provider what they offer or recommend.
  2. If you have a medical alarm, tell both the alarm provider and the phone provider before you switch. Some medical alarms do not work over standard VoIP at all and need a different arrangement. Some providers also offer Priority Assistance for people who rely on a landline for safety reasons, so ask whether you qualify.
  3. Keep a charged mobile as backup, and make sure everyone in the house knows the landline will not work in a blackout.

Alarms are the trap here. If yours reports over the old phone line, it may have gone quiet already: our guide to an alarm that stopped working after the NBN covers how to test it and the 4G fix.

What to sort before the switch

  1. Ask your provider where the handset plugs in: the NBN box phone port, a router, an adapter, or an app.
  2. Arrange to port your existing number, with the new provider, before cancelling the old service.
  3. Decide handset against app, or both, and get any adapter you will need.
  4. If anyone relies on a medical alarm or monitored alarm, tell both providers and confirm it will still work.
  5. Sort battery backup for the NBN box and router if the phone matters in an outage.
  6. Keep a charged mobile, and make sure the household knows the blackout limitation.

The short version

On the NBN your home phone is VoIP: it runs over your internet, not a copper line. Check with your provider exactly how the handset connects, some use the NBN box's phone port, others a router, an adapter, or an app, port your existing number instead of cancelling it, and above all plan for power cuts: without battery backup the phone dies in a blackout, which matters for medical and monitored alarms. Sort that list before your connection date.

Connection types, provider options and medical-alarm compatibility vary. Confirm the details with your phone provider, and check with your alarm provider before switching if anyone relies on the landline.

Related guides

Switching to the NBN and not sure what to keep?

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