The "Crystodyne" zinc oxide negative resistance electronic oscillator circuit invented by Russian scientist Oleg Losev around 1923. Experimenting with the first crude point-contact semiconductor diodes, called crystal detectors, Losev found that a diode made of a zincite (zinc oxide) crystal touched lightly with a steel wire when forward biased had negative resistance and would oscillate in this circuit. The resistor and battery apply a forward bias of 4 to 30 volts. The capacitor and inductor form a tuned circuit. The negative resistance of the diode cancelled the positive resistance in the tuned circuit, exciting sinusoidal oscillations. This circuit could oscillate at frequencies up to a few megahertz.