A rebuild control unit splits a rebuild process into partial processes and instructs an access processing unit to execute the partial processes. Preferred features include: the inner container being flush with or recessed below the plane to avoid interference during nesting; a hinged cover; and equal acute angles between a main-container endwall and the plane and an inner-container wall and the inner-container top. The method and apparatus is proposed for the use to diagnose and potentially prevent the incidence of POVL and anaesthesia awareness in patients during medical procedures. The IRF comprises a function for determining which SDP that shall store the subscriber data and the IRF thereafter transfer the subscriber data to the SDP. The system being also capable of producing audible surround sound and adapted to compensate for head motion through use of an optical based tracking system.