a beam tetrode in which the electrodes are part of resonators that constitute input and output oscillatory systems. A resnatron is designed as a heavy, demountable, water-cooled, metal tube, and gases are continuously evacuated from the interior of the tube. The resonators are two sections of coaxial line that are open at one end and short-circuited at the other. By varying the length of these lines, the natural frequencies of the resonators can be altered. Resnatrons were manufactured and used during the 1940’s and 1950’s to amplify and generate high-power oscillations—up to 85 kilowatts continuously and up to several hundred kilowatts in a pulsed mode in the decimeter range. They were later replaced by more modern tetrodes (seeMETAL-CERAMIC TUBES).