What type of electrical diagram for the autotransformer type motor controller is shown in the illustration? Illustration EL-0012

Correct Answer: Option D — The diagram is a ladder or line diagram (schematic).

Ladder or line diagrams use horizontal rungs to trace electrical control circuits and interlocks logically. According to IEEE 45 standards, this format is essential for marine engineers troubleshooting complex motor controllers like autotransformer starters because it displays electrical sequence rather than physical wiring layouts.