Is just sending a normal analogue phone call with your existing handset or cordless phone, through a digital converter or router into your Broadband Internet connection, and to the normal PSTN or analogue phone of another person.
This technology bypasses the phone exchange, as it’s passing through a Broadband connection, Cable or ADSL. So it is not registered by your phone carrier as a phone call. Using this system you can now make calls extremely cheap.
There are many companies offering many different solutions, from free software to VIOP routers. Temora Computers and Upside Down Websites has been using VIOP since 2005 and has helped many businesses and homes implement this service.
Temora Computers uses a SPA3102 for our VIOP, that just plugs into the router and uses a Panasonic 3 hand set cordless phone system
Temora Computers could demonstrate this in your offices or home if required.