Ok, actually, I misspoke with regards to the older EPIRBs.

"Older EPIRBs did not contain the GPS receiver, so the GOES satellite received only a serial number. To locate the EPIRB, another set of satellites (like the TIROS-N satellite) orbiting the planet in a low polar orbit could pick up the signal as it passed overhead. This would give a rough fix on the location, but it took several hours for a satellite to come into range."

If equipped, the search aircraft can also "look" for the signal from the EPIRB as they fly.

From the USCG:
http://www.navcen.uscg.gov/marcomms/gmdss/epirb.htm