Cathode Ray Tube or CRT monitors are the oldest form of display for PC Computer systems. These monitors are high resolution monitors and continue to be the technology of user’s choice today also. Most monitors use Cathode ray tubes, which are glass vacuum tubes into which an electron gun emits a flow of electrons. The electron gun is made up of cathode (negatively charged) and one anode (positively charged). The operation of a CRT monitor is basically very simple. A heating element in CRT heats the cathode and the cathode emits electrons. An image is displayed by scanning the electron beam across the screen and this image needs to be refreshed continually. In order to avoid any kind of fluctuation or flicker of screen, most monitors refresh the screen at a 60 Hz rate.