In November 1904, he invented and patented the two-electrode vacuum-tube rectifier, which he called the oscillation valve. It was also called a thermionic valve, vacuum diode, kenotron, thermionic tube, or Fleming valve. This invention is often considered to have been the beginning of electronics, for this was the first vacuum tube. Fleming's diode was a vital unit in radio receivers and radars for many decades afterwards, until solid-state electronic technology took over.
In 1906, Lee De Forest of the USA added a control "grid" to the valve to create a vacuum tube RF detector called the Audion, leading Fleming to accuse him of copying his ideas. De Forest's device was shortly refined by him into an amplifier tube called the triode. The triode was vital in the creation of long-distance telephone and radio communications, radars, and early digital computers.