I have the Globalfix, which has the built-in GPS. When you activate it, it turns on the GPS receiver and in a few minutes it knows your position. It includes that position in the signal it transmits.
The other one plugs in to your ship's GPS and monitors your progress. When you activate the EPIRB
, it includes your last known position in the transmitted signal. If you don't have the ship's GPS turned on, it doesn't get updated. On my boat, the fixed GPS is a chartplotter
that I rarely use (I use a handheld at the helm), so the EPIRB probably wouldn't know where I was.