Telephony Goes Digital (VOIP)

Scientists, never content with two tin cans and a string, looked for different ways to transmit sounds over long distances. The pioneering work of Harry Nyquist in the 1920s gave us the basics of sampling theorem. In the 1940s, Claude Shannon would mathematically prove Nyquist’s sampling theorem. Their work is the foundation for what we now call digital networking. Basically, they proved that you could take the analog signals of any POTS call and convert them to digital form. This meant that POTS calls could originate in analog form, be converted to digital form, and be transmitted on the PSTN using the now familiar ones and zeroes of computers. Digital networking had arrived, setting the stage for the beginning of VoIP.
The work of Nyquist and Shannon led to many telephone and computer network inventions. For example, Nyquist is credited with the patent that led to the first coder-decoder, or codec, device. Codecs can come in many sizes and shapes and are often found in the electronic circuitry of large networking devices. Codecs basically convert analog signals to digital form and vice-versa. Nyquist’s work led to the design of many other networking devices such as dial-up modems, high-speed broadband modems, IP routers, and VoIP gateway servers.
The ability to convert analog signals to digital form also led to the development of several types of computer networks. From the early 1960s to the present day, several types of digital networks, including fiber-optic-based networks and wireless networks, have emerged in support of computers and telephone systems. Today’s digital networks, regardless of the form they take, are capable of supporting VoIP telephony. We cover network types beginning in topic 4.