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Cheap Ball Mouse

Mouse
Mouse

Cheap old style ball mouse. PS/2 interface.

Top Removed
Top Removed

Top removed from the mouse, the ball fits in the gap in the centre. The slotted discs are visible which contact the ball & move relative to the surface the mouse is on.

PCB
PCB

PCB removed from the shell. Pairs of IR LEDs & Phototransistors make rotary encoders with the slotted discs. The microswitches read the mouse buttons & wheel.
IC in the centre interfaces with the PC over a PS/2 connection.