VoIP Extensions A VoIP looks and works just like a regular phone You can connect extensions using regular landlines and mobiles or VoIP (VoIP Over IP). VoIP is a technology which allows you make phone calls over a computer network. We support connection of User Extensions using VoIP technology. The phones sit on your desk and work just like any business phone. The only thing your VoIP extension needs to work is a broadband connection. Calls are then bridged over the Internet to your desk phone. This also means you can take your extensions anywhere there's broadband!.