Enable or disable the screen lock which will prevent any input from the keypad from being registered, with the exception of the START button which can still be used to create markers. 

When enabling the screen lock the display will show the combination of keys to press to unlock the screen. 

Once activated, the screen lock will automatically enable 60 seconds after the last key press or when the power button is pressed once. This allows you to select a screen to display and then manually lock it using the power button.