Which statement about normally intensified rungs on a PLC display is correct?

• A. They indicate the instruction is true and has logic continuity
• B. They indicate an error in the ladder logic
• C. They indicate the instruction is false
• D. They indicate the rung is disabled

Answer: (A)

A rung that is intensified on a PLC ladder display shows that the conditions on that rung are true and that there is a complete path for current to flow to the output. In ladder logic, each rung links input devices (contacts) to an output (coil). When all the required input conditions are satisfied, the rung becomes energized, and the display highlights it to indicate logic continuity from the left rail to the right rail. This visual cue helps you quickly see which parts of the circuit would operate at that moment. It does not indicate an error, nor does it mean the rung is false or disabled—the energized state specifically means the instruction would be executed and the coil would energize.