A stylus includes a timer; a signal generator coupled to a stylus tip; a switch; and a controller comprising one or more computer-readable non-transitory storage media embodying logic. The logic is operable when executed to: in response to the switch of the stylus being ON, initiate the signal generator to generate a signal having a pre-determined frequency and a pre-determined voltage from the stylus tip, and activate the timer, and stop the generating of the signal when a timing of the activated timer reaches a pre-determined threshold.