A CRT (Cathode Ray Tube) display unit is a commonly used output device. It displays the data or information received from the computer. The CRT screen is similar to a TV screen and it is a vacuum tube.
An electron beam is produced by the electron gun located at the back portion of the tube. The electron beam is directed towards the front of the CRT screen.
A coating of Phosphor material is made on the inner surface of the screen. The phosphor emits light when it is struck by electron beam. The color of the emitted light depends on the phosphor substance used.
A CRT display may be either monochrome (i.e. only one color) or color (i.e. multicolor).
Monochrome displays are available in green, blue, orange, yellow, pink, amber, red and white color.
Color displays are produced on CRT screen on the same principle as they are produced on color TV screen. To produce color display three phosphors: Red, Green and Blue are used.