What is a complete horizontal line in a ladder logic program commonly referred to as?

• A. Rung
• B. Segment
• C. Ladder
• D. Channel

Answer: (A)

In ladder logic, a complete horizontal line from the left power rail to the right side that carries the input conditions and produces an action on the output is called a rung. It represents a single control operation: when all conditions along that line are true, the output coil on the right is energized. Rungs are the basic building blocks of a ladder diagram, and many of them stacked vertically form the full program. The name fits the ladder metaphor because each rung acts like a rung on a ladder, connecting the two rails and enabling a path for power.

Other terms don’t fit this specific element. A segment isn’t the standard term for a horizontal line in ladder logic, the whole diagram is referred to as the ladder, and channel is more about pathways for signals or communications, not the individual horizontal line that controls a output.