English: Crude experimental wireless apparatus with which British music professor David Edward Hughes transmitted radio waves in 1879, 7 years before Hertz's proof of their existence. The apparatus consists of a spark transmitter attached to a clock (right), which transmitted a regular string of spark pulses, and a modified version of his carbon microphone (acting in a similar the roll to later devices called coherers) with which Hughes detected the pulses. Hughes set the transmitter running, then left his apartment with the receiver to see how far these "aerial waves" would go; he detected the pulses up to 500 yards from the transmitter. Hughes demonstrated his wireless "electric wave" transmission to a number of Royal Society scientists in 1880 who (incorrectly) told him the phenomenon was due to induction. Hughes, who was not a scientist, was unable to provide an alternate theory of transmission and accepted their explanation. Hughes' experiment did not come to light until 1899, 11 years after Heinrich Hertz published his proof of the existence of electromagnetic waves.
The apparatus had been abandoned in Hughes tenement and was found in 1922.