🔍 Key Concepts

• GMDSS distress and safety communications structure (sea areas A1–A4) • Purpose of on-scene communications versus initial distress alerting • Correct frequencies/modes associated with DSC, NBDP (SITOR), and VHF Ch-16

💭 Think About

• Think about which channels/frequencies are normally used to coordinate SAR (search and rescue) once the initial distress alert has already been sent. • Identify which options mix a calling/distress channel with a data/telex mode and ask whether that combination is actually used for on‑scene voice coordination. • Consider whether very high HF frequencies or special working channels (like VHF 22) are typically used for general on‑scene distress coordination in GMDSS.

✅ Before You Answer

• Verify which VHF channel is internationally designated for distress, safety, and calling. • Check which specific NBDP (SITOR) frequency around 2 MHz is identified in GMDSS for distress and safety communications, and compare the exact kHz values given. • Confirm whether HF 21.820 MHz is a standard GMDSS distress/on‑scene frequency or mainly a working frequency band.