Bubbles, Belts, and Bulbs: How the Scantron Works

The Scantron machine operates without software or a keypad, relying instead on two rocker switches and early 1990s chips inside its control board. A lightbulb shines through six reading sections while belts and motors move answer sheets past the device for grading. Testing confirms that only #2 pencils work correctly among pens Sharpies colored pencils and other pencil thicknesses tried by SimonRetro.