A gate below an elevator car which prevents access to an elevator hoistway. A controlling unit selects a filtering content to be applied to the block image data based on the encoding types of the block image data to be filtered, and a filtering unit applies filtering to the block image data to be processed according to the filtering content selected by the controlling unit. The remap window corresponds to the PCI memory address range. A portion of the subset still needing additional programming is identified. The front end has a jacking type screw which enables one to exert sufficient pressure so that the greater than 200 IO pins at the connector end are easily forced into receiving sockets. The present phase retarder makes it possible to conduct uniform polarizing conversion within a wide wavelength range using a single plate.