What number will a ship station use to identify itself using SITOR (NBDP)?

The identification of a ship station using SITOR (Selective Identification of Transmission for RTTY) or NBDP (Narrow Band Direct Printing) requires a specific number format that allows for proper communication and identification in maritime contexts.

The correct answer indicates that the ship station would use a five-digit SELCAL code or a nine-digit SELCAL number that is identical to the Maritime Mobile Service Identity (MMSI). This is crucial because SELCAL serves as an automatic calling system, enabling coast stations to signal specific ships without the need for continuous watchkeeping.

Using the SELCAL format ensures that the station can effectively communicate with other vessels and shore stations, allowing for reliable and efficient contact in various scenarios. The reliance on a number identical to the MMSI promotes consistency across different communication systems, enhancing safety and operational efficacy.

This option ties together a ship's identity with both its operational capabilities and international standards, which underscores why it is the most appropriate identification method in the context of NBDP.