In short
A VoIP phone system is a business phone system that makes and receives calls over an internet connection using voice over internet protocol, instead of analogue or ISDN lines. It gives each user an extension and number on desk phones, softphones and mobile apps, and adds menus, groups, queues and voicemail managed from a web portal.
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The short answer
VoIP (voice over internet protocol) is a way of sending voice as data. A VoIP phone system uses it to do everything a traditional business phone system does, without copper phone lines: it answers calls, routes them to the right person or team, lets people transfer and park calls, and connects you to every landline and mobile in the UK and abroad.
So when people ask "what is a VoIP call?", the answer is simply a phone call carried as data packets over a network rather than as an electrical signal over a dedicated line. To the person you are talking to it is just a phone call, whether they are on a landline, a mobile or another VoIP system.
If you want the mechanics, our guide to how a VoIP phone system works walks through a call step by step.
The four parts of a VoIP phone system
Every business VoIP phone system, whichever platform it runs on, is made of the same four parts:
- Numbers: your main number, direct dial numbers for people and teams, and any 03 or 0800 numbers. New numbers can be issued, and existing ones can usually be ported in. See VoIP numbers for business.
- The phone system: the software that applies your rules, sometimes called an IP PBX. It holds extensions, menus, hunt groups, call queues, opening hours and voicemail. See PBX vs VoIP.
- The connection: your broadband or leased line, your office network, and the link between your phone system and the public phone network, such as a SIP trunk or a Microsoft Calling Plan. See SIP vs VoIP.
- Devices: desk phones, cordless handsets, conference phones, headsets and softphone apps on laptops and mobiles. See VoIP handsets for business.
VoIP compared with a traditional phone system
A VoIP phone system does the same job as the phone system it replaces, but almost everything about how it does it has changed:
| Traditional phone system | VoIP phone system | |
|---|---|---|
| How calls travel | Analogue or ISDN lines from the exchange | Data packets over your broadband or leased line |
| Where the phone system lives | A box in a comms cupboard | In a provider's data centre, or as software you host |
| Where people take calls | Desk phones wired to the system | Desk phones, laptops, mobiles and Teams or Webex, anywhere |
| Adding a user | Often an engineer visit and new wiring | A few changes in a web portal |
| Several sites | A separate system or private links per site | One system shared by every site and home worker |
| Numbers | Tied to lines at an address | Held by the provider and pointed wherever you need |
| Power cuts | Basic analogue phones drew power from the line | Phones and network equipment need power or a UPS |
The power point matters. Openreach notes that digital lines need power, and anyone who depends on their landline, for example for a personal alarm, should tell their provider, who can offer battery backup. VoIP vs landline for business and our explainer on the VoIP landline go into the detail.
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Hosted or on-site VoIP
The phone system part can run in two places. In a hosted (cloud) VoIP phone system, a provider runs the software in its data centre and you simply connect devices over the internet; nothing sits in your comms cupboard apart from your router and switches. In an on-site or self-hosted system, you run the phone system software yourself, on a server in your building or in your own cloud account, and connect it to the phone network with SIP trunks. Most new business systems are hosted, and our sister site explains hosted VoIP phone systems in depth, while PBX vs VoIP compares the options side by side.
Business VoIP phone system benefits
These are the reasons most organisations move to VoIP:
- Work from anywhere: the same extension rings a desk phone, a laptop and a mobile app, so hybrid and mobile staff stay reachable on their business number
- Quick changes: add a user, change a menu or set a holiday message in a web portal, without an engineer visit
- More features as standard: menus, hunt groups, call queues, voicemail to email and mobile apps are part of most platforms, with call recording and reporting on the higher tiers
- Integrations: calls can pop up customer records in your CRM and sit inside Microsoft Teams or Webex
- Several sites on one system: offices, branches and home workers share one set of extensions and one call plan
- Ready for digital lines: VoIP does not depend on the analogue and ISDN lines that are being retired
Our VoIP phone system features page shows which features come with which platform tier, and VoIP vs landline for business sets out the comparison with traditional lines.
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What a VoIP phone system needs
VoIP is only as good as the network under it. Before you switch, check these:
- A reliable connection with enough upload capacity: Cisco puts a G.711 or G.722 call at about 87.2 kbps in each direction, including Ethernet overhead, and a G.729 call at about 31.2 kbps, so multiply by your busiest number of simultaneous calls and leave headroom
- Low delay: Cisco summarises the ITU-T G.114 recommendation as up to 150 ms of one-way delay being acceptable for most users
- A network that prioritises voice, using quality of service and often a voice VLAN; see VoIP QoS settings
- A router and firewall set up for VoIP, which often means turning SIP ALG off; see VoIP router
- Power for your network: routers, switches and Power over Ethernet phones need power, so plan a UPS where phones must keep working in a power cut
The full checklist is on our VoIP requirements page. If your connection needs work, our sister sites cover broadband for VoIP and leased lines for VoIP.
The VoIP phone systems we supply
Forever Systems supplies 3CX, Microsoft Teams Phone, Webex Calling, Forever Group's own Forever UC and Forever Teams platforms, and SIP trunks. BT Cloud Voice is supplied by our sister company Forever Communications through cloudvoice.cloud.
Because we supply several platforms, we can recommend the one that fits how your people work. Contact us and tell us a little about your team.
How Forever Systems helps you choose a VoIP phone system
We supply and support several VoIP platforms, so we can recommend the one that fits how your team takes calls rather than fitting your business around one product.
- Platform advice across hosted 3CX, Microsoft Teams Phone, Webex Calling, Forever UC and Forever Teams, with SIP trunks for phone systems you already own
- A requirements check of your broadband, network and routers before anything goes live
- Numbers and porting: we can help you keep your existing business numbers and plan the move away from analogue and ISDN lines
- Handsets and headsets that suit each platform, bought outright or, in some cases, included in your monthly rental, with the options confirmed at quote
- Set-up and changes: call flows, users and devices configured for you, and help with moves, adds and changes afterwards
- For BT Cloud Voice, see our sister site cloudvoice.cloud, and for hosted and cloud platforms in depth, cloudphone.cloud
We work with businesses, schools, charities and public sector organisations.
Frequently asked questions
What does VoIP stand for?
VoIP stands for voice over internet protocol. It is the technology that turns speech into data packets and sends them across an internet or private network, so phone calls can travel over the same connection as your other data.
What is a VoIP call?
A VoIP call is a phone call carried as data over a network instead of over a traditional phone line. VoIP calls can reach any landline or mobile number, because the provider connects them to the public phone network.
Is a VoIP phone system the same as a landline?
No. A landline carries calls over a dedicated line from the exchange, while a VoIP phone system carries them over your internet connection. You can keep your landline numbers on VoIP, and a digital landline is itself a simple form of VoIP. See VoIP vs landline for business.
Is VoIP the same as a hosted phone system?
Not quite. VoIP is the technology that carries the calls. A hosted phone system is a complete business phone system run by a provider in a data centre, which uses VoIP to reach your devices. VoIP can also run on a phone system you host yourself.
Do VoIP phones work in a power cut?
Desk phones, routers and switches need power, so they stop in a power cut unless you have backup power such as a UPS. Softphone apps on charged mobiles can keep working over mobile data, and calls can be diverted to mobiles.
Do I need a special phone for VoIP?
You need an IP phone, a softphone app, or an adapter for an analogue phone. Many businesses use apps on laptops and mobiles for most staff and desk phones only where they are needed, such as reception.
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