A logic test having less over-head for testing a logic circuit in a chip is implemented by constituting a test circuit in the chip without introducing a novel device process of FPGA. In an embodiment of the invention, the centrifugal clutch includes a clutch cover, a pressure plate for applying a clamping force against a friction plate, and at least one flyweight that moves radially outward under the effects of centrifugal force to cause the pressure plate to exert a clamping force against the friction plate. The plane phase of the polygon mirror in the first and second stations is controlled and central positions of image patterns by two laser beams are detected to correct the misregistration between these central positions. A system may include a client application program stored on a client computer, a network, and a server software program on a destination computer. The scan chains may be configured as a single group providing a test response to a single input signature register or a set of groups providing a test response to a multiple input signature register. The metadata may further include disc information and title information common to the discs, and the search unit may create the disc library using the disc information, the title information, and the volume information, and search for the desired audio-visual data using the created disc library.