Which of the following is NOT a type of digital display technology?

The choice that indicates a technology that is not categorized as a digital display is based on the nature of the display technology's operation. CRT, or Cathode Ray Tube, is an older display technology that relies on analog methods. It operates by firing electrons onto a phosphorescent screen, producing images as a result of the electron beams striking different phosphor compounds. This process fundamentally differs from digital technologies, which operate using discrete values to represent image information.

In contrast, LCD (Liquid Crystal Display), LED (Light Emitting Diode), and Plasma displays are all digital technologies. LCDs work by manipulating light through liquid crystals; LEDs use semiconductor materials to emit light; and plasma screens generate images through the use of small cells containing ionized gas that emits light when electrically charged. These methods set them apart from CRT as they utilize digital signals to create images, making CRT the only option in this question that does not belong in the same category as the others.