🔍 Key Concepts

• Recognize the schematic symbol used in figure B and match it to the listed semiconductor devices. • Note that the output in figure B is labeled 10–50 VDC, not AC, and consider which devices are typically used as low-side DC switches in PLC outputs. • Compare how a mechanical relay (shown in figure C) differs from the solid‑state symbol in figure B.

💭 Think About

• Look closely at the symbol in figure B: how many junctions or terminals are clearly shown, and does it look more like a transistor, a relay, or a bidirectional AC device? • Which of the listed devices is normally used as a DC low-side switch with the emitter (or equivalent terminal) connected to ground? • Which device type would more commonly be used for AC loads (like in figure A) versus DC loads (like in figure B)?

✅ Before You Answer

• Verify which choice corresponds to a three‑terminal transistor device commonly drawn with an arrow on one leg in schematics. • Eliminate any devices that are normally used for AC switching (especially bidirectional AC) since figure B clearly indicates a DC output. • Confirm that the chosen device type is commonly used in PLC output cards to switch DC loads by sinking current to ground.