A position input system includes a touch screen, an active stylus and a driver. The driver transmits an uplink signal to the active stylus via the touch screen in a current touch period, the uplink signal containing timing information that informs the active stylus of timing of a next touch period in which the active stylus transmits a downlink signal to the driver via the touch screen. In another embodiment, the driver transmits an uplink signal to the active stylus via the touch screen in a current touch period of a current frame at a time different from a corresponding touch period of a previous frame.