Which statement about equipment for sound signals is TRUE?

The statement regarding manual sounding of the signals being mandatory is accurate because the International Regulations for Preventing Collisions at Sea (COLREGs) emphasize the importance of ensuring that vessels can communicate their presence and intentions through sound signals at all times. This is particularly crucial in situations where visibility is limited, such as fog or heavy rain, when visual signals may not be sufficient to ensure safety.

Manual sounding capabilities ensure that operators have control over the signaling process and can respond to specific situations as needed. While automated systems may be convenient, they are not a substitute for the ability to manually sound signals, especially in emergency situations where quick, precise communication is essential for avoiding collisions.

The other options, while they may contain elements of truth, do not accurately reflect the key requirement for sound signal equipment. Redundancy in electric signaling is not universally mandated, nor is it stated that sound signals are optional in clear weather since they remain a critical safety measure regardless of visibility conditions. As for the preference for automated signals, the rules prioritize the reliability and manual control of sound signaling to ensure effective communication among vessels.