As shown in the illustrated block diagram for a programmable logic controller system, what functional component is used to interpret inputs, carry out program instructions, and communicate decisions as action signals to outputs? See illustration EL-0225.
• In a PLC (Programmable Logic Controller), different modules have distinct roles: some handle field signals (I/O), some handle communication with other systems, and one acts as the "brain" that executes the program. • Look at how the illustration labels the I/O modules versus the module that the arrows from inputs and to outputs pass through logically. • Think about which module would actually run the control logic (ladder diagram) that you download from the programming unit.
• From the diagram, trace the path conceptually: field devices send signals into which type of module, and which component must make decisions before signals go out to actuators? • Ask yourself: which choice describes a module that doesn’t just pass signals, but actually executes instructions and decides what the outputs should be based on the inputs? • Which listed module would still be essential for decision‑making even if communication with other systems was lost?
• Verify which module in the picture is most closely associated with the Run / Scan / Fault indicators, since scanning the program is part of decision‑making. • Confirm that input and output modules mainly convert and condition signals, rather than interpret the logic of the program. • Make sure the module you choose is the one that would still be needed if you already had separate input, output, and communications modules in place.
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