|The Fleming tube image
The British phycisist John A. Fleming discovered that the Edison
effect could be used for the detection of the Hertzian waves.
Basically Fleming used an electric lamp whose filament was surrounded
by a cilindrical plate. Since such device could control the
flow of current in a circuit, in analogy to a valve in a water pipe
system it was named also as a valve.
Unfortunately the Fleming valve later known as a diode was still
unable to amplify the feable electric signals detected by the aerial.