If the sound signal (horn) is not working, it is considered to be what?

When a sound signal, such as a horn, is not operational, it is classified as inoperable. In maritime practice, having a functioning sound signal is crucial for safety, as it is used to communicate intentions and warn other vessels, especially in restricted visibility. If the horn fails to operate, it cannot be relied upon for these important communications, which directly affects the safety of the vessel and its crew.

The choice of being "under maintenance" suggests that repairs or adjustments are actively being made, which is not the situation if the horn simply does not work at all. Similarly, the term "functioning intermittently" implies that the horn might work at some times and not others, which would not provide the reliability needed for safety at sea. Lastly, the option of being "safe" would inaccurately suggest that a vessel can operate without a crucial safety feature.

In summary, the classification of the sound signal as inoperable accurately reflects its inability to perform its safety function, indicating a need for immediate attention or repair.