🔍 Key Concepts

• DSC (Digital Selective Calling) distress alert structure and order of components • The phasing signal purpose in DSC transmissions • The standard bit length of the alternating dot pattern that comes before the phasing signal

💭 Think About

• Think about the sequence of elements in a DSC distress alert: call setup, distress format, and what is transmitted immediately before the phasing signal. • Consider why an alternating dot pattern is used and how long it must be to allow the receiving equipment to synchronize properly. • Compare the answer choices as powers or multiples of 2 and think which length is commonly standardized in digital signaling for synchronization.

✅ Before You Answer

• Verify in the GMDSS/ITU DSC documentation the standard bit length of the alternating dot pattern before the phasing signal. • Check that the chosen bit length is explicitly associated with synchronization just prior to the phasing signal in a distress alert. • Confirm you are looking at the section describing distress alert format, not routine or urgency calls.