The pioneering work of Heinrich Hertz and Guglielmo Marconi on wireless communication at the turn of the 20th century led to aggressive research of electronics, transmitters, and detectors. Hertz and Marconi worked with very poor detectors (spark gap detectors and coherers respectively). In 1901, J.C. Bose's discovered a very simple detecting circuit that consisted of an LC circuit and a new device. The new device consisted of a thin metal wire (called a catwhisker) contacting a semiconducting lead sulfide crystal. This discovery was quickly followed by discoveries of similar behavior with silicon carbide and silicon detectors. The new circuits, known as crystal radios, were intensively studied in the following decades.

The catwhisker device was very similar to what is now known as a Schottky diode. In the early 1900s, semiconductor physics did not exist, and the success of crystal radios was due exclusively to trial-and-error and luck. The catwhisker is still constructed sometimes by do-it-yourselfers who want to make crystal radios in their homes (see