a protective device for a glazed structure , in particular an aircraft windscreen 20 , comprises at least one removable sacrificial sheet of transparent composite 10 . the composite 10 comprises a transparent polymeric film 11 having on one side an electrically conductive layer 12 formed from a dispersion of electrically conductive particles and which is coated with a transparent hard coat 13 , with the other side having adhesive layer 14 thereon . sheets of the composite 10 may be arranged in a stack so that each sheet adheres to the adjacent underneath sheet with the uppermost sheet of each stack being removable as the sheet becomes damaged and / or dirty .