Abstract: A system for changing the display direction of a screen includes a gravity sensor, a control key unit, a display control unit, and a control mode choice unit. The gravity sensor is adapted to generate gravity-sensing signals according to the orientation of the screen. The control key unit is adapted to generate a control instruction. The control mode choice unit is connected to the gravity sensor and the control key unit. The control mode choice unit is adapted to send either the gravity sensed signal from the gravity sensor or the control instruction from the control key unit to the display control unit. The display control unit is adapted to control the display direction of the screen according to either the gravity sensed signal or the control instruction.

Abstract: A system for generating click input signal for optical finger navigation, includes a touch sensor, a timing unit, and a control unit. The touch sensor is adapted to sense whether a finger presses thereon. The timing unit is adapted to time a duration time of the finger pressing on the touch sensor when the finger presses on the touch sensor. The control unit is adapted to generate a first click signal when the duration time is greater than a threshold value and generate a second click signal when the duration time is smaller than a threshold value.