EPIRB
Emergency Position Indicating Radio Beacon

PLB
Personal Locator Beacon

ELT
Emergency Locator Transmitters


Are EPIRBs with the capability to deploy automatically in the event of a disaster at sea.

Category II EPIRBs
Are similar to Category I EPIRBs but are generally manual deployment only.

Class B EPIRBs
also called Category B or "Mini B", operate a 121.5 MHz homing signal only and are usually manual deployment only units.  The International Cospas-Sarsat program will no longer monitor Category B EPIRB signals as of February 1, 2009. The U.S. Coast Guard no longer recommends them.

NOAA
National Oceanic and Atmospheric Administration

Category I EPIRBs