A rotatable device, such as a pulley, includes an annular rotatable member having a bore extending therethrough and an outer surface disposed about the bore. The seat back includes a front support surface for supporting the seat occupant in an upright seating position. The first air recovery inlet is provided to cross the center line. The first direction and the second direction are substantially perpendicular to a direction of setting the accessory part to the mirror housing, respectively, and substantially perpendicular to each other. Then, the address forwarding table is analyzed according to the media access control address, so that an assigned number of a port of the network switch is acquired.