Mechanical mouse:-

The ball mouse replaced the external wheels with a single ball that could rotate in any direction. It came as part of the hardware package of the Xerox  Alto computer. Perpendicular chopper wheels housed inside the mouse's body chopped beams of light on the way to light sensors, thus detecting in their turn the motion of the ball. This variant of the mouse resembled an inverted trackball and became the predominant form used with personal computers throughout the 1980s and 1990s. The Xerox PARC group also settled on the modern technique of using both hands to type on a full-size keyboard and grabbing the mouse when required .the ball mouse has two freely rotating rollers. These are located 90 degrees apart. One roller detects the forward-backward motion of the mouse and the other the left-right motion. Opposite the two rollers is a third one (white, in the photo, at 45 degrees) that is spring-loaded to push the ball against the other two rollers. Each roller is on the same shaft as an encoder wheel that has slotted edges; the slots interrupt infrared light beams to generate electrical pulses that represent wheel movement. Each wheel's disc has a pair of light beams, located so that a given beam becomes interrupted or again starts to pass light freely when the other beam of the pair is about halfway between changes. Simple logic circuits interpret the relative timing to indicate which direction the wheel is rotating.  The driver software in the system converts the signals into motion of the mouse cursor along X and Y axis on the computer screen.

                      

Parts of a mechanical mouse:-

1.    Left mouse button/ select button

2.    Middle button / scrollbar

3.    Right mouse button/ properties button

4.    Signal cable

5.    Microcontroller.

6.    Optical wheel (x-axis)

7.    Optical wheel (y-axis)

8.    Track ball

9.    Support spring wheel

1    Electrolytic capacitor

1    Resistors