Ok Jeff,
I agree that the distress function of the RADIO using DSC is important,
but for this, any gps can send the position of my boat to the radio, so
that the mayday buttom works. I was saying that the polling function of
the radio, for position report on my gpsmap276c is much less usefull
than a AIS function. The position report can tell me the position of
others boat only when ruested by the polling function, so I must know
the mssi code of the boat; I think this can be usefull to a flotilla
cruising or maybe to fishing boats, or a race comitee. To have the
position of a mayday boat in the gps ploter is not so usefull, because
it is rare fact, and a sailboat or any leisure boat has little to do an
a mayday function, contrary to ships or CG duties. The AIS main value
from a sailboat perspective is Colision avoidance, and in this regard,
a AIS transponder with a AIS receiver would be better, but a AIS
receiver only would be vey usefull .

Concluding, I think that the ideal solution would be a VHF/DSC/AIS
ready radio, wich could receive the AIS signal of all ships for
colision avoidance using litlle 12 V charge, but in a danger situation,
I could activate the transmit function to send automactic to all ships
my position (uses more 12V). The AIS NMEA message received could be
send to my Gps/Ploter wich would plots the ships position etc, like
others softwares does (ShipPloting, SeaClear, MaxSea, SeaPro etc), and
providing other important information like CPA/TCPA etc.

Regards

Pascal