Doctor Who - The Tenth Doctor's Sonic Screwdriver Includes a hidden UV pen & UV light which reveals your secret writing Button activated lights & 'Sonic Screwdriver' sound effects Requires 3x AG13 Batteries (included) Flip open the cap at the end of the Screwdriver to reveal an additional button that activates the light and sound effects when it is in full extension OPEN mode. Pressing the button on the side of the handle activates the LED and Sound FX which operates in CLOSED mode.