Lots of good sites with mostly good information,
http://searoom.com/dsc-radios-and-mmsi/ . Here is the statement that is confusing to me: "DSC calls can be made directly to another vessel without broadcasting; it is much more private, like making a phone call. Remember, a DSC call does not use Channel 16. If the call is directed to an individual station, then that signal is sent on Channel 70 and only that station receives the call."
After your comments I now see where this is only a private hail to speak (and/or exchange location) on a designated open airwave channel. I guess that's better than using C69 and saying hey Bud let's go chat on 78.
My new Standard radio has the ability to "nav to" (point) to the DSC's location. Similar functions with AIS. Tried the AIS yesterday and saw various ships positions. I would be unable to "nav to" via the radio since I am 1 wire short on the GPS for hooking up this feature, which not sure I would ever use anyways as long as I can see their position.