Abstract: There is provided a magnetron comprising a cold cathode having an electron emitting member which is formed linearly or as a plane on a substrate to emit electrons a subdivided anode disposed oppositely in parallel with the electron emitting member, the subdivided anode having cavity resonators formed therein at the side of the cold cathode, and a magnet which producing a magnetic field lying at right angles to an electric field applied between the cold cathode and the subdivided anode. There is also provided a microwave oven for dielectric-heating a substance to be heated by using the magnetron as a microwave supply source.

Abstract: A video signal recording/reproducing device has at least a frequency modulating unit which FM modulates information to be recorded on an optical disk memory, a laser driving pulse generating unit for generating a laser driving pulse derived from the frequency-modulated signal generated by the frequency modulating unit and for modifying the duty factor of the laser driving pulse in accordance with the linear velocity of the optical disk memory where recording is taking place; and a recording unit for controlling the laser power during recording to an optimum value in accordance with the linear velocity of the optical disk memory where recording is taking place. This arrangement enables reduction of the minimal length of recording bits resulting in reproduced signals of a level sufficient for obtaining reproduced images of a fine quality addition enables increase of the recording capacity of the optical disk memory.