Abstract: The invention relates to the activation and automatic inactivation of keys on a mobile telephone terminal keypad, wherein the terminal includes a display and key depression sensing means. A time parameter denotes the length of time that has passed since a key was last pressed and is set to zero by means adapted to this end, and counting-up of the value of the time parameter is commenced subsequent to setting the time parameter to zero. The time parameter is compared with a threshold value (Tlock) and automatic inactivation of the keys in the keypad is initiated immediately the time parameter exceeds the threshold value (Tlock). An appropriately selected key is kept activated for activation during that time in which the keypad is in an inactivated mode, and the terminal is set to a stand-by mode.