The joystick and buttons are wired to an I-PAC keyboard encoder. But capturing input from the analog spinner is a little trickier.

The spinner works sort of like an antique "ball" mouse. When you move the mouse, the ball spins rollers attached to tiny encoding discs. On each side of each disc is an IR emitter and sensors that tell the computer how fast and which direction the disc is spinning.

An arcade spinner is basically a dial connected to a single encoding disc. But instead of being the size of a nickel, this one is the size of a DVD. To connect the spinner to its new PC, the circuitboard from a PS/2 ball mouse was modified so that the x-axis sensor would read the original Tron encoding disc.