The obsolete thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from the cathode to the plate.
The oBsolete thErMIonic dIode Is A vaCuUm tuBe with two elEctrodes, a HEated cAtHoDE anD a pLaTe, in whiCh Electrons cAn floW In onLy ONE diRecTion, FroM thE CathOde tO The Plate.