How does it work? - CRT television

How does it work? - CRT television

This animation demonstrates how a CRT television works.

Technology

Keywords

CRT television, television, TV, cathode ray tube, diode, TV tuner, transistor, pixel, resolution, terrestrial broadcasting, satellite broadcasting, cable television, TV station, electrical signal, electromagnetic, remote control, technology, physics

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Scenes

  • - When they hit the phosphor layer covering the back of the screen they cause fluorescence: the phosphor emits light. The intensity of the light depends on the strength of the electron beam. The strength of the electron beams, bent by the deflection coils, are controlled by the electronics. In colored TV sets each pixel is composed of three phosphor dots, a red, a blue and a green one. Each dot is hit by a separate electron beam.
  • - It is composed of three phosphor dots, a red, a blue and a green one. When the electron beams hit the phosphor dots, they emit light (fluorescence). The intensity and the color of the light depends on the strength of the electron beam.

Narration

A cathode ray tube (or CRT) is a vacuum tube consisting of an electron gun and a screen. The back of the screen is lined with a layer of phosphors. When an electron beam hits this layer, it causes fluorescence there, that is, the phosphors emit light. The intensity of the light emitted by a given point depends on the strength of the electron beam.

The electron beam is emitted by the electron gun. The electric current inside the deflection coils creates a magnetic field that directs the electron beams so that they scan the layer of phosphors covering the back of the screen line by line. The strength of the electron beams constantly changes, thus the strength of light emitted by pixels also changes and an image is created.

The layer of phosphors in the screen consists of pixels. In color CRT screens, each pixel consists of three phosphorus cells. These emit blue, red or green light when hit by electron beams. Each phosphor cell is hit by a separate electron beam, which is why three electron guns are necessary in color CRT television sets.

The screen frequency refers to the frequency of the electron beams scanning the screen per second. The value is 50 Hz for television sets, while in computer monitors it is typically higher at 60-130 Hz.

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