| 摘要 |
An apparatus having dual modes and adapted to control a position of a cursor on a display screen comprises a ball capable of being put in a rotation for determining the position, a roller device in contact with the ball to detect the rotation of the ball, a shell having thereon an opening to protrude therefrom the ball and accommodating therein the ball and the roller device, and a cover mounted on and connected to the shell, extractable therefrom to shield the ball from being inadvertently contacted, and retractable to be received therein to permit the apparatus to be normally used. This invention provides a simple apparatus capable of functioning as either a track ball or a mouse used for controlling a cursor on a display screen, e.g. a monitor.
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