(2) Light Pen

A light sensitive pen which is used as a pointing device is called a light pen. Whenever a light pen tip is placed against the CRT screen, it is capable of sensing its position on the CRT ( Cathode Ray Tube ). As the tip of the light pen is moved over the surface of the screen, its photo cell ( light sensitive element ) detects the light emitted from the screen.We can choose the desired option of the menu by touching light pen against desired option.

A Light Pen

A light pen can be used for drawing directly on the CRT screen while using Computer Aided Designing (CAD) package.