What does the term 'rung' refer to in ladder logic programming?

In ladder logic programming, the term 'rung' specifically refers to a horizontal line that connects conditions to outputs. Each rung represents a unique logic operation in the control process, where the left side typically contains one or more input conditions (such as sensors or switches) that, when met, will activate the output represented on the right side of the rung (such as a motor or light). This arrangement resembles a ladder, which is where the name comes from, and the rungs are executed from top to bottom.

This structure allows for a clear visualization of how inputs interact to control outputs, making it easier for programmers to design and understand control circuits. Therefore, understanding the concept of a rung is fundamental for anyone working with ladder logic in programmable controller systems.