• Cathode Ray Tube (CRT) display is a visual display unit (VDU)
  • Huge size & heavy weight. Used in desktop computer
  • Portable computer use LCD- light weight, small size & ruggedness

CRT monitor, 

  • receives video signal from computer
  • displays it as dots on CRT screen

Components:

  • CRT (cathode ray tube) or Picture tube
  • CRT is an evacuated glass tube with fluorescent coating on screen. 

Working

  • Electron gun emits  electron beam towards screen – Phosphor coating produces illumination – exist for few millisec.
  • Deflection is by elecro magnetic deflection
  • Horizontal Deflection coils
  • Vertical deflection coils
  • Form permanent image – repeated illumination

Raster Scan

  • Electron beam moved back & forth on screen
  • On reaching right, brought to left
  • On bottom, brought to top
  • To produce an image, beam is turned off or on
  • Uses video info from computer
  • HSYNC – Provides horizontal sync (left to right)
  • VSYNC – for vertical sync
  • Colour monitors popular than monochrome monitors

CRT Monitor Block Diagram

Types of Images on CRT Display:

  • Graphics

  • Alphanumeric displays – follows dot matrix scheme

Interfacing Methods

  • TTL Video Interface – Sends Video, HSYNC & VSYNC on separate wires
  • Composite Video Interface – Mixed signals sent as composite waveform