Telephony: A Background

The idea of transmitting voice communication data over wires was first mooted in 1667 when Robert Hooke’s experiments in sound transmission resulted in the string telephone. Many children are still taught the fundamentals of sound waves transmitted through vibrations with this device, which can be made quite simply by attaching a tin can to either side of a length of a string.

It would take another two centuries before the human voice could be transmitted and captured through electrical wires. Philipp Reis developed the first device that could transmit and receive acoustic sounds in 1861. To demonstrate its capabilities, he tested it with music, but also the difficult phrase “Das Pferd frisst keinen Gurkensalat” (The horse does not eat cucumber salad). Alexander Graham Bell, however, managed to develop the technology around 1876 that could transmit speech more clearly over distances, and Thomas Edison would later develop the telephone networks that would make this technology usable for the masses.

Through most of the early part of 20th Century, voice telephony was transmitted over copper cables. The next revolution came in the 1930s when radio transmission joined the party. Electronic switching arrived in 1965, and the first communications satellites were also launched.

Digital technology caused another major revolution that allowed for the development of the Internet, using the same communications networks that were used for voice calls. The fact that we can now make voice calls over data networks has its roots in the development of Voice over IP (VoIP) technology in the late 70s. Although the technology is old, it would take a while before consumer Internet bandwidth increased to a level suitable for making the technology usable. One of the biggest drawbacks is delays between sending and receiving, which can make communication hard. Another is packet loss — if the connection quality is bad, some data packets fail to be transmitted successfully, resulting in garbled audio.