Telephony Goes Digital

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  con- vert 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 net- work 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 develop- ment of several types of computer networks. From the  early 1960s to the  pre- sent 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.