A fault tolerant network switch includes two or more switches units and a highly reliable interconnect unit so that during normal operation both switches are actively handling network packets and upon the failure of one of the switch units, another switch unit takes over, ensuring continued normal network operation, with somewhat reduced performance. A pixel electrode is formed on the top surface of the first insulating substrate. A sheet media is transported between the intermediate transfer member and the impression drum while the intermediate transfer member and the impression drum are disengaged. The program is executed to control the motion of the CCD sensor. The operation unit performs predetermined operations of the bits of these effective dynamic range to obtaing an operation result.