Im afarid Orrissails post is very misleading
Lets review some terminology
Pushing the red button ( all radios should have a 5 secs delay as mandated by COMSAR)
this called a "undesignated distress
alert". Its so as you do not have the option of indicating the nature of the distress
Next up , is a "designated distress alert ", this is activated from the menus, involves picked an distress designation ( flooding etc) and the distress alert is activated from the menu.
All this is followed up by a voice Mayday procedure.
As correctly point out the US only ( nobody else allowed them) SC101 radios, can't follow the proper procedure. But lets stay with Class D
ANybody with a DSC
class A radio
can acknowledge a DSC distress alert. But normally its the coastguard and everyone must wait to allow them to do so.
Next up is a "Urgency call", this is the DSC equivalent to Pan Pan. Its activated from the menu, its normally sent to the MMSI of the closest CG radio
station. Its followed up by a Voice Pan Pan, the Urgency call does not have a auto repeat function
After that we have normal DSC calls , either to specific, or group MMSIs