4256A58G01 is an integrated high-density digital mixed I/O card within Westinghouse Emerson 4256 series Ovation WDPF distributed control system, matched with 4256A25 MRC main remote control boards and 4256A26 remote expansion boards for remote I/O rack assembly. This all-in-one module integrates digital input signal collection and digital output drive control functions simultaneously. For input channels, it gathers field discrete feedback signals such as valve limit positions, equipment contact status and interlock switch signals with optoelectronic isolation and signal filtering. For output channels, it receives logic instructions from the DCS main controller to drive field actuators including relays, solenoid valves and contactors, realizing bus signal decoding and power amplification. It combines DI and DO circuits on a single board to reduce the total number of cards and save cabinet space for sites with balanced input and output point counts. Every channel features independent opto-isolation design to avoid cross-talk interference between input and output loops. It is fully plug-and-play compatible with all supporting MRC and expansion boards, requiring no system configuration adjustment during replacement.