Which of these would not be a bad outcome of an Urgency DSC call to all vessels specifying an alternate TELEX frequency & emission that cause your transceiver to automatically switch?
• DSC (Digital Selective Calling) procedures for urgency calls (MAYDAY vs PAN-PAN) • Role of the DUS (Distress/Urgency/Safety) table/placard and what frequencies/modes your equipment is allowed to auto-select • Differences between J2B (telex/NBDP) and J3E (SSB radiotelephony) emissions and when auto-switching is acceptable
• For each option, ask: would this automatic switch put my radio on a frequency and emission that my ship is actually authorized and set up to use for distress/urgency/safety traffic? • Think about what the DUS table/placard is there to prevent. Which scenarios show that control working properly, and which show it being bypassed or ignored? • Consider whether it is safer for the set to switch only to combinations (frequency + emission) that are both: (1) on the DUS placard and (2) appropriate for the type of traffic requested (telex vs voice).
• Verify how your equipment is required to use the DUS table/placard for automatic frequency changes on receipt of DSC distress/urgency/safety calls. • Check which emission designator (J2B vs J3E) is used for TELEX/NBDP traffic and which is used for voice, and match that to what the urgency DSC call is asking for. • Confirm that auto-switching to a non‑placarded or non‑marine band frequency would be considered improper or dangerous.
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