Which is a potential indication that a GMDSS station is not operating correctly?

The scenario of a sudden change in modulation from voice to silent mode can indicate a malfunction in a Global Maritime Distress and Safety System (GMDSS) station. GMDSS equipment is designed for reliable communication, particularly in emergencies. A sudden change to silent mode suggests that the equipment may not be responding correctly or could be experiencing technical difficulties.

Maintaining consistent operating modes is crucial for effective communication. Voice mode allows for verbal interaction, which is necessary for clarifying information and assuring the parties involved of the nature of the situation. If a GMDSS station suddenly shifts to silent mode without operator intervention, it raises the concern of potential issues with the equipment's function—such as software glitches, hardware malfunctions, or power problems—making it a clear indication that the system is not operating correctly.

In contrast, while the inability to communicate with nearby vessels during safety drills or frequent interruptions to transmissions is important, they may not always indicate a malfunction but could be due to operator error or environmental factors. Similarly, constant voltage changes might reflect normal electrical fluctuations rather than a system fault. Thus, the abrupt mode change serves as a more direct signal of a malfunction.