The horizontal lines connect the rails to the logic expressions. Each ______ is numbered in ascending sequential order.

The horizontal lines connect the rails to the logic expressions. Each ______ is numbered in ascending sequential order.

• A. Rails
• B. Contacts
• C. Signals
• D. Rungs

Answer: (D)

In ladder logic diagrams, the horizontal segments are called rungs. Each rung forms one step of the control logic, linking the left power rail to the right return rail through the components placed on that rung. Those rungs are numbered in ascending order from top to bottom to provide a reference for diagnosing and documenting the program. The vertical lines are the rails, not the steps that get numbered, and the individual switch elements inside a rung are called contacts. So the thing that gets sequential numbers is the rung.

In ladder logic diagrams, the horizontal segments are called rungs. Each rung forms one step of the control logic, linking the left power rail to the right return rail through the components placed on that rung. Those rungs are numbered in ascending order from top to bottom to provide a reference for diagnosing and documenting the program. The vertical lines are the rails, not the steps that get numbered, and the individual switch elements inside a rung are called contacts. So the thing that gets sequential numbers is the rung.