Which of the following is NOT a component of a ladder diagram?

In a ladder diagram, which is a representation used primarily in electrical control schematics, the essential components include inputs, outputs, and rungs. Inputs represent control devices that provide signals to the system, typically switches or sensors. Outputs are the devices that act upon the signals, such as motors or lights. Rungs are the horizontal lines that depict the control circuit, connecting the inputs and outputs in a way that illustrates how the system operates.

Transistors, while they can play a role in certain applications within control systems, are not a fundamental component of ladder diagrams. They are more often associated with electronic circuits and may not be explicitly represented in the graphical form of ladder logic, which focuses on relay control principles. Thus, identifying transistors as not being a component of a ladder diagram aligns with the core elements that define this type of schematic, which does not inherently include them as standard parts.