🔍 Key Concepts

• GMDSS distress, urgency, and safety priorities and how they are sent on HF • The difference between ARQ (Automatic Repeat reQuest) and FEC (Forward Error Correction) in SITOR/NBDP • When you would use broadcast versus two‑way (point‑to‑point) modes for distress and safety messages

💭 Think About

• For a distress or safety message that needs to reach many ships and coast stations at once, which type of mode (ARQ or FEC / SSB voice or print) is better suited for broadcasting? • When communicating directly with a single coast station (like the U.S. Coast Guard) on a known working channel, which mode supports acknowledged, error‑checked two‑way telegraphy? • Look carefully at the answers that forbid switching modes; does GMDSS generally restrict you from using a more effective mode after initial contact if conditions change?

✅ Before You Answer

• Identify which option correctly matches ARQ with two‑way, acknowledged telegraphy and which matches FEC/SSB with broadcast use. • Check which choices incorrectly limit your ability to change from FEC to ARQ when it would improve communication. • Verify which answer clearly supports the GMDSS goal of maximum reliability and widest possible reception for distress/safety messages not going only to one coast station.