🔍 Key Concepts

• HF (High Frequency) coast radio station identification practices • Difference between call sign, MMSI (Maritime Mobile Service Identity), and subscriber number • How traditional voice radio vs digital selective calling (DSC) identify stations

💭 Think About

• Ask yourself: when you listen to voice communications on HF or VHF, what form of identification do you most often hear spoken aloud? • Which of the options is specifically tied to GMDSS DSC rather than normal voice calling procedures? • Which identification method has historically been used long before digital systems like MMSI existed?

✅ Before You Answer

• Verify which method is spoken over the air in plain language/letters/numbers during normal HF voice calls. • Confirm which identifiers (MMSI, MID) are primarily used for digital signaling and coding, not routine spoken identification. • Make sure the chosen option matches standard ITU Radio Regulations practice for coast stations using HF voice.