For those who didn’t know: EPIRB = Emergency Position Indicating Radio Beacon. Sends an emergency signal via satellite and terrestrial RF. They can be triggered manually, but they also trigger automatically if salt water shorts two exposed pads for a certain amount of time (a minute, I think).
Once triggered it will get a GPS fix and transmit a distress signal via satellite as well as terrestrial VHF. It is programmed with the MMSI of the ship it belongs to.
Works all over the world, although they take a bit longer to successfully transmit the signal in the polar regions as they then have to rely on LEO sattelots in polar orbits.

Source: I have a GOC, and I also used to work with marine electronics. I’ve programmed hundreds of these. Mainly Jordan Jotron TR60 (Ducking autocorrect). Some from McMurdo too, don’t remember the model name.

Fun fact: A coworker did have to make the phonecall of shame to the coastal radio after accidentally dropping one overboard.