Do I need a phone line for VoIP?

A traditional landline bundles two things. One is the copper pair that runs from the building to the phone company. The other is the voice service the company delivers over it: dial tone, a number and a path to other phones. VoIP replaces the second. Whether you still have the first depends on how your internet arrives.

DSL is where the confusion starts, because it sends data over a telephone wire. A business on DSL has a phone wire in use and may have no phone service on it at all. Fiber, cable and mobile data don't use that wire. In each case the VoIP call travels as data, and the company that provides the connection doesn't have to be the company that provides the calls. We compare the options in what type of internet connection you need for VoIP.

So dropping analog phone service doesn't mean there's no wire and no bill. A business that wants calls to and from public numbers still needs a connection and a calling service, whether they arrive on one invoice or two.

The device decides whether any analog equipment is involved. An IP phone looks like a desk phone and plugs into the data network. A softphone is an app that uses the microphone and speaker of a computer or mobile phone. Neither needs a phone jack.

An analog handset can stay in service through an adapter. The adapter gives the handset an analog line to plug into and converts the audio to packets on the other side. RFC 3435 describes this kind of device as a gateway that provides a traditional analog interface to a VoIP network. A compatible handset can make and take basic calls this way. Features beyond that depend on how the adapter is configured and on the provider. We explain the port types in what a PSTN gateway is and what FXS and FXO ports do.

IP phones need the same check. Atlantech Online's business phone service shows the range a provider supports: a headset connected to a computer or mobile phone, handsets it supplies, or your own device if it works with its voice switch. Its FAQ says the service supports most SIP-compliant VoIP phones, and it recommends models from an approved list for full feature support. A phone that connects isn't guaranteed every feature. There's more on handsets in whether you need a special phone for VoIP.

Calls from one app to another can work with no connection to the public telephone network. Microsoft Teams is an example. Microsoft's calling overview says native calls between Teams clients are processed by its cloud services. Making and receiving outside telephone calls takes a connection to the public network and Teams Phone licensing as well.

So the service is what joins your VoIP calls to everyone else's phone numbers. How it reaches you varies. Atlantech offers a cloud PBX, where the phone system runs on its side and your phones and apps connect to it. For a business that keeps its own PBX, it delivers service by SIP, by PRI or as analog. So an older phone system with PRI or analog ports doesn't have to be replaced before you change who provides the calls.

Keep the old service running until your number has moved. A number transfers to the new provider by porting, and Microsoft's port order guidance for its calling plans says inactive or disconnected numbers can't be ported. The same page warns that broadband associated with a ported number is disconnected automatically once the port completes. That's Microsoft's process, and other providers have their own. The dependency is worth checking with any of them. If your internet is bundled with the phone line you're giving up, sort out the connection before the port.

Look for devices connected to the old line that nobody thinks of as phones. A fax machine, an alarm panel or an elevator phone on that line needs something to plug into once the line is gone. Whether it works through an analog gateway depends on the device and on how it's monitored, so check each one with its supplier. Atlantech's POTS replacement service is built for this case. It's a managed appliance that gives those devices analog ports, supports two to eight lines and connects over broadband, 4G LTE or both. We list the equipment to check in which legacy devices are at risk when POTS lines are retired.

Emergency calling changes as well. If you use a VoIP phone or app away from the address it was set up for, the service needs the location where you are calling. How it works out the location sent with a 911 call depends on the service. Where it relies on an address you registered, that address has to be kept current. We cover that in whether you can dial 911 from a VoIP phone and how to register a VoIP phone for 911.

Power is the last change to plan for. The UK government's guidance on the move to digital landlines explains that an analog line carries a low-voltage supply from the telephone exchange, enough to run some basic corded handsets through a local power outage. Suppose your VoIP setup is an IP desk phone and a router plugged into wall power. Both stop in a power outage unless backup power covers every powered device between the phone and the connection. Backup inside the building keeps your own equipment running. It doesn't keep the provider's network running if the outage reaches that too.