🔍 Key Concepts

• Trouble relay location and symbol in the lower schematic (right side, near the alarm light and buzzer bus) • How alarm light and buzzer behave in normal (no-fault) versus fault conditions • Meaning of normally open (NO) vs normally closed (NC) contacts on a relay symbol and how they are drawn relative to the de‑energized coil

💭 Think About

• First, decide: in normal, healthy operation with all navigation lights working, should the alarm light and trouble buzzer be energized or de‑energized? How does that choice affect whether the relay contacts must be open or closed in the normal state? • Follow the wiring from the supply bus, through the trouble relay contacts, to the alarm light and buzzer bus. When the relay coil is energized, do these paths complete the circuit to turn the alarm devices on, or do they remove power from them? • Look at how many separate contact sets are drawn around the trouble relay symbol. Are they shown as open or closed when the coil is at rest, and what happens to the alarm circuits if one lamp fuse blows?

✅ Before You Answer

• Verify which state on the drawing represents the relay de‑energized (normal drawing state) and remember that is what "normally open" or "normally closed" refers to. • Confirm that there are two separate contact symbols associated with the trouble relay, both changing state together when the coil is energized. • Double‑check whether, in the fault condition (blown fuse/lamp), the alarm light and buzzer should receive power or lose power; then match that behavior to the choice that describes those relay contacts.