This is a standalone unit with a built in GPS and a dedicated rail mounted antenna. It is extremely low power and when the options are set right (to our taste), it sounds alarms rarely when we don't want to know. We like not having AIS target clutter on our chart plotter.

Around Puget Sound, there is a lot of shipping going at "ocean speed" so, when we're out crossing the Sound under sail, it is nice to get its prediction of a closest point of approach.

Only once have I been especially glad to have it. We were sailing toward the East Cape area of the Baja Peninsula broad reaching, preventer set, middle of the night, and we picked up a freighter coming our way. They were 15 miles away or so, and we watched the CPA. It was mostly predicting 4 miles or less. That was not a crisis but we were able to call the freighter by name. There was a bit of a language barrier so it took a few tries to get our request through, pointing out that we could not alter our course and speed a whole lot. They happily altered course a few degree to give us an assured bit of extra separation. We didn't need an automatic DSC link to the VHF transceiver to make that happen.

Other times, the AIS is a source of entertainment, helping us to learn more about vessels around us. Most of the time we don't REALLY need it.