Voice over Internet Protocol (VoIP) allows users to make phone calls by using the Internet rather than using the traditional public switched telephone network (PSTN). Internet telephone calls are converted from an analog voice signal to digital format and then compression/translation of the signal into Internet protocol (IP) packets for transmission over the Internet, with the process being reversed at the receiving end. This technology was introduced by Vocaltec Inc in February 1995 when it introduced Internet Phone software. According to the IEC, the minimum system requirements to run the initial program was a 486/33-MHz (or higher) personal computer (PC) equipped with a sound card, speakers, microphone, and modem.
This original software would only work if both parties are
using Internet Phone software, which would occupy internet bandwidth. Thanks to
major companies like Vonage, Ooma, and MagicJack, VoIP users can now call
land line phones and even cell phones in other countries for a fixed monthly or annual
fee. This breaks from the norm of land line
companies charging by the minute with varying rates for different
countries. Although this technology has great advantages, it has also
received its fair share of criticism.
Mainly competing companies such as AT&T, who offer traditional public
switched telephone network long distance (PSTN) calling. They brought up issues of loss of service during
power failures, internet malfunctions, and PC problems as their largest
disadvantages. They claimed that these
issues contributed to some people dying, due to issues with contacting 911 in
emergencies. However the majority of the
people using VoIP were using it primarily for long distance calling, and either
had cell phones or traditional land line phones to call 911.
Wikipedia: Voice over Internet Protocol