http://wikiless.i2p/wiki/Alexander_Stepanovich_Popov?lang=en
After receiving a signal, the metal filings in the coherer had to be reset by a manually operated vibrator or by the vibrations of a bell placed on the table nearby that rang every time a transmission was received. [ 7 ] Popov set to work to design a more sensitive radio wave receiver that could be used as a lightning detector , to warn of thunderstorms by detecting the electromagnetic pulses of lightning strikes [ 1 ] using a coherer receiver. [ 1 ] [ 2 ] Operating principle [ edit ]...