How should you read a ladder diagram?

• A. Left to right, top to bottom
• B. Right to left, bottom to top
• C. Top to bottom, left to right
• D. Bottom to top, right to left

Answer: (A)

In ladder diagrams, you trace the path of power from the left rail through the elements to the right side of each rung. You evaluate rungs starting at the top and moving downward, and within each rung you check the elements from left to right. If everything along the path in a rung is true, the output coil on that rung is energized. This left-to-right flow within a rung combined with top-to-bottom progression of rungs is what determines the final state of outputs. That’s why the reading order is left to right, top to bottom.