DE3929141A1 Sep 2, 1989 Mar 14, 1991 Hopt & Schuler Ddm Card monitoring device esp. for reader - has aperture blocking device coupled to read head preventing unauthorised tamperingDE3929141A1 * Sep 2, 1989 Mar 14, 1991 Hopt & Schuler Ddm Card monitoring device esp. for reader - has ...