What best represents "On-scene" communications?

The correct choice represents "On-scene" communications specifically in the context of maritime operations. SITOR (Simplex Telex Over Radio) as a form of Narrowband Direct Printing (NBDP) is particularly suited for on-scene communication due to its ability to provide reliable, error-free text-based communication. When operating on the established frequency of 2174.5 kHz, vessels in proximity to an incident can exchange important information or updates in real-time, which is essential in emergency scenarios or in coordinating search and rescue operations.

Utilizing this method is particularly beneficial because it can transmit messages automatically, allowing for efficient communication under conditions where voice communication might be challenging. This capability aligns closely with the needs for immediate, precise, and clear communication on-scene in maritime emergencies.

In contrast, the other options either involve communications systems not specifically tailored for on-scene scenarios or operate on frequencies that may not be optimal for the immediate exchange of crucial information during such operations.