EPIRBs (pronounced ee-pirbs), officially known as Emergency Position Indicating Radiobeacons, transmit digital radio beacons on the international distress signal frequency 406 MHz. Designed to work with satellites, EPIRBs are detectable by COSPAS-SARSAT satellites, which orbit the poles, and by the GEOSAR system which consists of GOES weather satellites and other geostationary satellites.
EPIRBs, detected by the GEOSAR system, send rescue authorities an instant alert, but without location information unless the EPIRB is equipped with an integral GPS receiver. EPIRBs detected by COSPAS-SARSAT satellites provide rescue authorities the location of distress, but the distress alert and the location can sometimes be delayed as much as an hour or two.
If you registered your EPIRB, when it is activated your registration information will be sent automatically to the appropriate Coast Guard Search and Rescue Coordinator Center (RCC). The Coast Guard will attempt to contact the owner/operator at the phone number listed in the database to determine if the vessel is underway. If there is no answer, they will attempt to contact family members using the emergency contact numbers you provide to find out the vessel's intended route, the number of people on board, etc. This is why you should always file a float plan with these contacts to let them know as much as possible about your voyage. The more information your contacts have to the give the Coast Guard, the better rescuers will be prepared to react and launch a search.
One of the best types of 406 MHz EPIRBs you can buy has an integral GPS navigation receiver that will send accurate location as well as identification information to rescue authorities immediately upon activation through both geostationary (GEOSAR) and polar orbiting satellites. The Coast Guard recommends you purchase a Category I EPIRB 406 MHz (if it can be installed properly) with an integral GPS navigation receiver. Alternatively, you can purchase a Category I or Category II personal locator beacon (PLB) to wear on your person. There are pros and cons to both EPIRBs and PLBs.
You must register new or used 406 MHz EPIRBs with NOAA. If you change your boat, your address, or your primary phone number, you MUST re-register your EPIRB with NOAA. If you sell your EPIRB, make sure the purchaser re-registers the EPIRB, or you may be called by the Coast Guard if it later becomes activated.
Further reading about EPIRBS and Personal Locator Beacons (PLBs):
How to Register an EPIRB or PLB
Should You Purchase an EPIRB or a PLB?
The Best EPIRBs or PLBs to Buy
Marine Electronics Review - SPOT Personal Locator Beacon
Marine Electronics Review - ACR Electronics AquaFix 406 I/O Personal Locator Beacon
Marine Electronics Review - ACR Electronics ResQFix 406 GPS Personal Locator Beacon
Marine Electronics Review - ACR Electronics GlobalFix iPRO EPIRB
