A protecting structure of an uninterruptible power supply prevents the uninterruptible power supply. With the method and apparatus, a unique identifier is created by a server process when the server process is started. In the direct filtering operation, signal characteristics of the stereo-channel audio signal are adjusted based on the crosstalk-cancelled virtual sound sources. In accordance to another aspect of the present invention, a low spin rate golf ball with an inner core and a thin dense layer disposed radially outside of the centroid radius is provided. The at least one cartridge may be adaptable to mimic at least one pathology of the human ear, such as an eardrum perforation, a middle ear fluid, a cholesteatoma, a tumor, or earwax.