🔍 Key Concepts

• Study how the typical navigation light circuit is wired, especially the path from the supply bus, through the 3‑amp fuse(s), to the stern light and to the alarm light / trouble relay. • Notice what condition actually triggers the alarm (buzzer and alarm lamp): is it loss of current through the stern‑light circuit, or something happening only in the alarm branch? • Compare a blown fuse with other possible open circuits in the same path. Any component that interrupts that monitored current will create the same indication.

💭 Think About

• When the stern‑light circuit fuse blows, what exactly changes electrically in the circuit—where does current stop flowing, and what does that do to the trouble relay and alarm light? • For each choice (A–D), ask: does this event remove current from the same part of the circuit that the blown fuse affects, or does it only affect the alarm/audible device itself? • Look closely at the two‑compartment running light symbol and the transfer switch. Which lamp is being monitored at that moment, and what happens if that lamp or its fuse opens?

✅ Before You Answer

• Identify which component the trouble relay is monitoring (the stern‑light load side, the fuse, or just the alarm branch). • For each option, decide whether the alarm devices (buzzer and alarm lamp) would still be able to operate if that component failed. • Make sure you distinguish between a failure that stops current to the stern light circuit versus a failure that stops current to the alarm circuit itself; only the former will truly mimic a blown stern‑light fuse.