A polishing head including, below a polishing head body, a rubber film held by a disk-shaped mid plate and an annular guide ring disposed around the rubber film holding the back surface of the workpiece on a lower face portion of the rubber film. The test circuit may include a test mode decoder circuit to enable a test mode and a data selector circuit to select at least a portion of data stored in the at least one write-only register as test data. The totaling screen displays a sum price of the purchased commodity, as well as choices of payment methods, \u201cCash\u201d and \u201cCredit card\u201d, and choices of reception of the commodity, \u201cTake out\u201d and \u201cDelivery\u201d. This decrypted digital file is capable of being used by a display logic to display an image of the object. This position information can be used to adjust suspension ride height as needed.