How does VoIP work?

Early on it was determined that it was possible to send a voice signal to a remote destination digitally, as well as via analog. To do that, we have to digitize it with an ADC (analog to digital converter), transmit it, and at the end transform it again in analog format with DAC (digital to analog converter) to use it.

This is basically the way VoIP works, sending voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public switched telephone network (PSTN). A major advantage of VoIP and Internet telephony is that it avoids the tolls charged by ordinary telephone service.