A communication device including a ground element, an antenna element and a switching unit is provided. Each blade or vane member has a plurality of relatively short 3D blades or vanes extending radially outward and an engaging edge of selected shape. The shaft is supported by two bearings which, in combination with the housing define a second housing chamber adapted to enclose means for monitoring andor controlling the brake and in this way, an integrated, compact controllable brake is provided. The tablespace instances restored from database backups are recovered to a particular point-in-time.