<P> In 1878, David E. Hughes noticed that sparks could be heard in a telephone receiver when experimenting with his carbon microphone . He developed this carbon - based detector further and eventually could detect signals over a few hundred yards . He demonstrated his discovery to the Royal Society in 1880, but was told it was merely induction, and therefore abandoned further research . Thomas Edison came across the electromagnetic phenomenon while experimenting with a telegraph at Menlo Park . He noted an unexplained transmission effect while experimenting with a telegraph . He referred to this as etheric force in an announcement on November 28, 1875 . Elihu Thomson published his findings on Edison's new "force", again attributing it to induction, an explanation that Edison accepted . Edison would go on the next year to take out U.S. Patent 465,971 on a system of electrical wireless communication between ships based on electrostatic coupling using the water and elevated terminals . Although this was not a radio system the Marconi Company would purchase the rights in 1903 to protect them legally from lawsuits . </P> <P> Between 1886 and 1888 Heinrich Rudolf Hertz published the results of his experiments where he was able to transmit electromagnetic waves (radio waves) through the air, proving Maxwell's electromagnetic theory . Early on after their discovery, radio waves were referred to as "Hertzian waves". Between 1890 and 1892 physicists such as John Perry, Frederick Thomas Trouton and William Crookes proposed electromagnetic or Hertzian waves as a navigation aid or means of communication, with Crookes writing on the possibilities of wireless telegraphy based on Hertzian waves in 1892 . </P> <P> After learning of Hertz demonstrations of wireless transmission, inventor Nikola Tesla began developing his own system based on Hertz and Maxwell's ideas, primarily as a means of wireless lighting and power distribution . Tesla, concluding that Hertz had not demonstrated airborne electromagnetic waves (radio transmission), went on to develop a system based on what he thought was the primary conductor, the earth . In 1893 demonstrations of his ideas, in St. Louis, Missouri and at the Franklin Institute in Philadelphia, Tesla proposed this wireless power technology could also incorporate a system for the telecommunication of information . </P> <P> In a lecture on the work of Hertz, shortly after his death, Professor Oliver Lodge and Alexander Muirhead demonstrated wireless signaling using Hertzian (radio) waves in the lecture theater of the Oxford University Museum of Natural History on August 14, 1894 . During the demonstration a radio signal was sent from the neighboring Clarendon Laboratory building, and received by apparatus in the lecture theater . </P>

The three stages in radio listening according to douglas ( early radio ) include