What is an MMSI number used for?

The Maritime Mobile Service Identity (MMSI) number is a unique nine-digit identifier assigned to a vessel or a shore station that is used in maritime communication. This identification plays a critical role in maritime navigation and safety, allowing vessels and shore stations to be distinctly recognized in communication systems.

The use of MMSI numbers facilitates various functionalities, including using them for Digital Selective Calling (DSC), which helps establish communication by automatically calling and identifying other vessels or shore stations with the unique MMSI identifier. This identification process enhances safety management by ensuring that the correct information reaches the intended recipient, particularly in emergencies.

While tracking maritime traffic is an essential part of modern navigation and safety, it is not the primary function of the MMSI number itself. Similarly, while boats need to be registered for operational and legal purposes, this is separate from the primary purpose of the MMSI. Sending distress signals is a critical feature in maritime safety, but the MMSI number specifically serves to identify and communicate the vessel or station.

Thus, the correct answer emphasizes the essential role of the MMSI in identifying maritime units within communication systems.