Devices used to create images in the form of light on a screen. Old televisions and monitors were made using this technology, which contains a vacuum tube, electron gun, and a fluorescent screen. CRTs are environmentally hazardous because they contain large amounts of lead, which is hazardous to the environment.

The cathode ray tube (CRT) is a vacuum tube containing an electron gun and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to form images in the form of light emitted from the fluorescent screen. The image may represent electrical waveforms (oscilloscope), pictures (television, computer monitor).