🔍 Key Concepts

• Digital Selective Calling (DSC) structure in GMDSS messages • Purpose of an error‑checking field in digital radio communications • How digital systems detect if the message has been corrupted in transmission

💭 Think About

• In a DSC message, what special part of the message helps the receiver detect transmission errors? • Looking at each option, which one actually sounds like a technical term for an error‑detection element in a digital signal? • Which options contain words that don’t typically appear in standard GMDSS or radio‑communication terminology?

✅ Before You Answer

• Verify which option best matches a known error‑detection code concept from digital communications (similar to parity bits, checksums, CRC). • Eliminate any option that uses unusual or non‑standard wording you’ve never seen in GMDSS/DSC materials. • Ask yourself: would this phrase realistically appear in an IMO or ITU manual as the name of a specific error‑checking character/field?