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• A pointing control device consisting of spherical ball, having some portion projecting above the surface.
• It is stationary and doesn't require more space.
• Used in military applications, video games and now in some new mobile phones like T-Mobiles, blackberry etc.

Working

• Consists of two valuators either potentiometers or shaft encoders that senses the rotations of the ball and supplies results proportional to its relative position.
• The ball is free to rotate in any direction.
• To move the pointer, user need to rotate the ball with your thumb, finger or palm of your hand and can click one of two buttons to select deselect the item.

Joystick

• A controlling device consisting of one or more buttons and a stick that is mounted in the base.
• Used in computer games and controlling machines such as cranes, trucks, aircraft etc.

Working

• Similar to trackball it consists of two or three valuators either potentiometers or digital shaft encoders.
• Valuators provides the result by varying the pressure, speed and direction of the stick.
• Joystick pointer or object keeps moving in the direction of the joystick pointing and stops moving when joystick returns to its upright position.
• Extra buttons and triggers are used to assign commands or initiate actions.