VoIP technology is a one way of sending a voice signal also known as an analog signal in a medium which is digital, i.e, the internet. In practice, the process works like this when you have a standard analog telephone attached to your high speed internet connection with VoIP service. There will be an analog telephone adapter or ATA between the phone and the computer.

In order to place what would normally be a long distance call to a person who doesn't have VoIP service you key in the number you want. The analog telephone adapter converts the touch tones into a digital format. The digital phone number is sent by the analog telephone adapter to the VoIP routing system at the service provider's location. The VoIP service provider is located on the internet as well.

The VoIP service provider's routing system identifies the recipient's location and sends the call to the Public Switched Telephone Network (PTSN) at that location. The phone rings at the other end and the conversation can begin. Each time you speak, the analog to digital converter in the analog telephone adapter changes the voice tones into packets of digital information that can be transmitted across the internet. When the VoIP service meshes with the Public Switched Telephone Network at the recipient's end, the digital packets which are the voice tones from you get turned back into an analog signal so that you recipient of your call can understand what you are saying.

The reverse process, i.e. the transmission of what the other person says to you is a mirror image of the first process. Their voice is transformed from analog to digital when it gets to the PSTN/internet connection. The digital packets are sent to the analog telephone adapter at your location where they are converted back into an audible or analog signal to be able to perceive the voice as that of your caller.

The technology to do the conversion from analog to digital and back again has been around as long as digital electronics. For example, your PC sound card converts digital CD information to analog signal needed by the speakers on your computer. The difficult part of the VoIP technology is the necessity to smoothly transmit the digital data over the internet and reassemble it in a continuous stream. This is know as the protocol.

When listening to voice transmission, there can be no gaps in the stream of digital packets or the voices will not be understandable. This part of the technology has only recently been available, but is actually equal or better in quality than you get with standard telephone networks.

The equipment available today that uses VoIP technology can be an analog telephone adapter for your head set through the computer. There are a few VoIP phones that act like a regular analog telephone but have the ATA incorporated into the phone. It's actually a small dedicated personal computer in your telephone. These VoIP phones can be plugged into the computer with high speed internet connection or into the router.