A cathode ray tube (CRT) is an analog display device that generates an image on a phosphor-coated screen using beams of electrons directed from an electron gun.
The cathode ray tube (CRT) was a foundational technology for visual displays in televisions, computer monitors, oscilloscopes, and various industrial instruments. At its core, the CRT operates by heating a cathode that emits electrons. These electrons are accelerated through an electric field and precisely directed using electromagnetic or electrostatic deflection systems to strike a phosphor-coated glass screen. When the electrons impact the phosphor, they cause it to emit light, creating the visible image.
Color CRTs use three separate electron guns, one each for red, green, and blue phosphors, allowing for the creation of millions of colors through precise beam alignment. This analog technology offered sharp, vibrant displays that defined broadcast and computing industries for decades. Although CRTs have largely been replaced by LCD, LED, and OLED technologies, they still see limited use in legacy equipment, specialized test instruments, and waveform analysis due to their high refresh rate and color fidelity.
Safety and environmental standards for CRTs, particularly concerning radiation and disposal, have been managed by agencies such as the U.S. Environmental Protection Agency (EPA) and international bodies including the International Electrotechnical Commission (IEC).
The cathode ray tube was first developed in the late 19th century, with Karl Ferdinand Braun inventing the early oscilloscope-style CRT in 1897. By the mid-20th century, CRTs became the dominant display technology in televisions and computer monitors. They remained a global standard until the early 2000s, when thinner, energy-efficient flat-panel technologies such as LCD and LED began to replace them.