was the first widely used detector for radio communication.
built upon the discoveries of Temistocle Calzecchi-Onesti, who demonstrated
in experiments in 1884 through 1886 that iron filings contained in an
insulating tube will conduct an electrical current under the action of an
operation of the coherer is based upon the large resistance offered to the
passage of electric current by loose metal filings, which decreases under the
influence of radio frequency alternating current.
coherer became the basis for radio reception, and remained in widespread use
for about ten years.