A guide to VoIP, the technology that lets you make voice calls over the internet

landline phone internet router and laptop — VoIP, or Voice over Internet Protocol, is a type of internet-connected phone system.
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VoIP (Voice over Internet Protocol) is a system for transmitting voice calls over the internet.
IP phones use an internet connection rather than phone lines for transmission, but otherwise work the same as traditional phones, including using area codes and phone numbers.
VoIP can be substantially less expensive and more secure than traditional landline phones.
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VoIP is shorthand for a telecommunication technology called Voice over Internet Protocol, and it's a modern alternative to traditional phones. For a century or so, landline telephone systems have carried voice data over a network called the public switched telephone network (PTSN). VoIP, on the other hand, allows voice calls to be transmitted over the internet. Your VoIP phone is simply a node on the internet with an IP address, much like your desktop computer.

Although VoIP phones work over the internet, they behave almost exactly the same as traditional landline phones – they use area codes and phone numbers, not usernames or passcodes.

It's also worth noting that even though your smartphone is an internet device and uses the cellular network to connect to the internet, phone calls you make with your voice plan are not VoIP – instead, cellular calls are transmitted using the voice cellular network. This is why most plans track voice and internet data usage separately.

How VoIP works

To use Voice over IP, you generally need a dedicated VoIP desktop phone (usually called an IP phone) which, instead of plugging into a phone jack, connects to the internet – usually by plugging into an internet router with an Ethernet cable or another form of high-speed internet connection.

To enable the phone, you need to subscribe to a service plan with a VoIP service provider. Generally, businesses have VoIP accounts which are substantially less expensive than traditional landline phone plans.

woman using landline phone in office — VoIP phones can be used in office spaces in place of landlines.
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When you dial a phone number using a VoIP phone, the phone sends packets of data to the internet, which is transmitted much like any other kind of internet data. The VoIP service provider sends the data from your phone to the phone that was dialed, where the data arrived and is turned back into audio information.

The advantages and disadvantages of VoIP

In general, VoIP is a substantial improvement over traditional landline services, but there are few obvious downsides to VoIP.

The advantages:

It's more reliable. While the PTSN has little redundancy and calls can be lost or incomplete if there are network issues, VoIP uses the internet, which is robust and can routinely work around outages and hardware problems.
VoIP can be significantly cheaper than landlines. Businesses like VoIP because it requires substantially less hardware to connect a large number of phones to the PTSN. Residential users can often get VoIP bundled with internet and cable TV for less money than a landline from a traditional phone provider would cost.
It's mobile. Because IP phones are simply internet devices, you can typically move an IP phone to any available Ethernet connection - it's not restricted to a specific desk or location. Even better, a VoIP user can generally use a compatible VoIP app on their phone to make calls when away from the VoIP phone.

The disadvantages:

You generally need a broadband internet connection. You don't need a lot of bandwidth for voice communication, but if your internet connection is below about 10Mbps, you can have problems with audio quality.
Internet connectivity issues can disrupt phone service. As a general rule, VoIP is highly reliable. But if you do have an internet connectivity problem, it can take out both data and voice at the same time. If you had a landline, it would probably not have been affected by the internet outage.
You might have issues with 911 services. The FCC requires that VoIP provider who fully connect to the PTSN provide emergency 911 services. But there are exceptions - not all VoIP systems need to be compatible with Enhanced 911 services - and there might be situations when a call to 911 does not automatically provide emergency services with your location.

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