An electron tube in which a beam of electrons can be focused to a small cross section and varied in position and intensity on a display surface. In common usage, the term cathode-ray tube (CRT) is usually reserved for devices in which the display surface is cathodoluminescent under electron bombardment, and the output information is presented in the form of a pattern of light. The character of this pattern is related to, and controlled by, one or more electrical signals applied to the cathode-ray tube as input information.