Editing Multiplexing (section)

===Telegraphy===
The earliest communication technology using electrical wires, and therefore sharing an interest in the economies afforded by multiplexing, was the [[electric telegraph]]. Early experiments allowed two separate messages to travel in opposite directions simultaneously, first using an electric battery at both ends, then at only one end.

[[Émile Baudot]] developed a [[time-multiplexing]] system of multiple [[David E. Hughes|Hughes]] machines in the 1870s. In 1874, the [[quadruplex telegraph]] developed by [[Thomas Edison]] transmitted two messages in each direction simultaneously, for a total of four messages transiting the same wire at the same time. Several researchers were investigating [[acoustic telegraphy]], a [[frequency-division multiplexing]] technique, which led to the [[invention of the telephone]].