In ladder diagrams, which class of components is positioned on the right as final outputs?

• A. Output devices
• B. Input devices
• C. Memory elements
• D. Power supplies

Answer: (D)

In ladder diagrams, signals are evaluated from left to right, with inputs and conditions on the left and the things that actually do something in the machine on the right. The right-hand side shows the final actuation, which are the output devices—coils, relays, contactors, motors, and other actuators that physically drive the system. Power supplies, while essential, provide the energy for the circuit and are typically represented as the left-hand rails feeding the rung; they are not the final outputs. Memory elements or internal relays can appear within the rung to store state, but the items on the far right are the actual outputs that perform the action.