electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelope

a vacuum tube in which a hot cathode emits a beam of electrons that pass through a high voltage anode and are focused or deflected before hitting a phosphorescent screen

a gas-discharge tube with a hot cathode; used in stroboscopes

a gas-discharge tube consisting of a cold cathode and a diode in a tube filled with gas; the color of the glow depends on the particular gas