🔍 Key Concepts

• Auto-alarm system operation on a ship’s radio receiver (what it is designed to respond to) • Function of a square-law detector in distinguishing the true alarm signal from other signals or noise • Role of the mechanical selector and what kinds of faults or conditions it is (or is not) meant to respond to

💭 Think About

• Ask yourself: Is the bell supposed to ring only for correct emergency alarm reception, or also for any electrical/mechanical fault in the system? • Think about a square-law detector: does it react to the specific modulation/pattern of an auto-alarm signal, or to general power problems like low voltage and open circuits? • For each option, decide: would that condition actually produce the alarm sequence at the detector/selector, or would it more likely prevent any signal from reaching the bell at all?

✅ Before You Answer

• Verify which condition(s) would allow the receiver and detector to still function well enough to produce the correct alarm pattern at the output. • Check whether low battery voltage, open circuits, or blown fuses are more likely to stop the system from working rather than trigger the alarm. • Confirm that the mechanical selector is driven by the received alarm signal characteristics, not by unrelated power-supply or wiring failures.