A sidebar to the article “Meet the mouse,” published in Personal Computing, issue 3/1983, pp. 103.

Inside Hawley’s mouse we find a ¾-inch stainless-steel ball (1). As the ball rolls across the desk, it transfers its x and y movements to two small cylindrical drums (2) resting on the ball at a 90-degree angle to one another. The rolling ball turns the cylinders in proportion to the extent and direction of travel. Connected to the ends of the cylinders are small code wheels (3) coated with alternating stripes of conductive and nonconductive material. As these code wheels turn, they deliver electrical pulses for each incremental rotation of the cylinders. Delicate wire fingers (4) resting on the code wheels decode electrical pulses generated by the conductive stripes and send them to the computer in a digital form it can read to track the mouse’s movement. The three buttons (5) on top are used to select from menus on the screen, edit text, and move symbols.