Digital Selective Calling uses VHF channel 70 for automated distress and calling functions. A properly registered MMSI identifies the vessel, and a connected position source can include coordinates.
The red distress control is not self-explanatory during panic. Register the MMSI correctly, connect and test the radio according to manufacturer and authorized procedures, and teach the crew what follows an alert.
After a DSC distress alert, use channel 16 voice communications when possible to provide the nature of distress and other details.