Module 4 - Safety
Distress Communications
DSC (Digital Selective Calling) can raise a distress alert on VHF Channel 70. Lift the cover and press and hold the distress control for the period specified by the set's instructions. The alert identifies the vessel by MMSI and can include position and time when the radio receives valid GNSS data; it carries the selected nature of distress, or an undesignated distress if none was selected, to DSC-equipped stations in range. Follow the alert with the voice MAYDAY on Channel 16.
A voice MAYDAY is normally broadcast on VHF Channel 16. The format is: MAYDAY MAYDAY MAYDAY — This is [vessel name ×3] — MAYDAY [vessel name] — My position is [lat/long or bearing and distance from known point] — I have [nature of distress] — I require [assistance needed] — [number of persons on board] — Over.
An EPIRB (Emergency Position Indicating Radio Beacon) transmits a 406 MHz distress alert via satellite when activated; GNSS-equipped units can include position. A radar SART helps rescuers home in at close range by appearing on compatible radar.
- DSC distress alert — hold the covered distress control as instructed; MMSI is sent, with position/time when available, then follow with voice MAYDAY on Channel 16
- MAYDAY — voice distress call on VHF Ch 16 for grave and imminent danger
- PAN PAN — urgency call (serious but not immediate danger to life)
- SECURITÉ — safety message (navigational or weather warning)
- EPIRB — satellite distress beacon
- Radar SART - close-range locating aid for compatible radar
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