https://books.google.co.uk/books?id=TNs3AQAAMAAJ&pg=RA3-PA7&lpg=RA3-PA7&dq=adnl&source=bl&ots=ykwRLKHoZv&sig=Dx2U8fi-2oug4iiVqjJ8CYzNIU0&hl=en&sa=X&ved=0ahUKEwjs5eHt-vfRAhXjK8AKHVg-C5UQ6AEITjAL#v=onepage&q=adnl&f=false

and the glossary...how interesting..."prevent them from finding out" replies BI ONLINE...lisa and block of wood had presumably wanted to concentrate upon high and low frequency transmissions...which they didn't want intercepting..."chip them so they can't..." - go figure: