I understand that technically DSC uses a reserved channel, channel 70 for digital connection.

Ultimately it sounds as if it is handy for someone using VHF and hailing others on a fairly regular basis. What confused me was DSC radios with a need for GPS vrs what AIS is. I did some reading at various sources and see that the GPS input for DSC is just to send your position (I believe) in case of emergency.

AIS on the other hand is a transponder system that allows your AIS equipped VHF to send your position data and receive data from others, showing relative positions and courses to all such equipped users. I know there is an A type for commercial vessels and B type (is that receive only, I'm still not sure?).

Of course the irony is that since all vessels don't have this, while you may know where that big heavy cargo ship is, some small fast private pleasure boat can still run into you in the fog... so the old MarkI eyeballs and ears are still the best thing going.

Do warships use AIS?

Also as I look around, apparently there is only one VHF that has built in GPS... STANDARD HORIZON GX1700, all the rest require a NEMA feed from a GPS. More stuff to tie together.

While I can see that one could have all their technology nicely tied together, GPS chartplotter, radar, AIS VHF, AP... one has to wonder if all this somehow gets in the way of just sailing. Now that said, yes, I have a basic VHF and a handheld GPS and even radar. I rarely turn on any of it. Perhaps in a crowded seaway, at night, with a fog... I might wish I had more info, and those of you sailing in and out of crowded ports might really need all of this technology to keep really safe.

Certainly the idea that a GPS VHF can send out a mayday with the push of one button sounds like great idea for "the rest of the crew," and is worth pursuing for that reason alone.