The old ones you got, probably won't work anymore.
Class A
121.5/243 MHZ. Float-free, automatically-activating, detectable by aircraft. Coverage is limited. These devices have been phased out by the FCC and may no longer be used, marketed or sold in the U.S..
Class B
121.5/243 MHZ. Manually activated version of Class A. These devices have been phased out by the FCC and except for certain devices used as personal locator beacons, may no longer be used, marketed or sold in the U.S..
Class C
VHF ch15/16. Manually activated, operates on maritime channels only. These devices have long been phased out by the FCC and may no longer be used, marketed or sold in the U.S..
Class S
121.5/243 MHZ. Similar to Class B, except it floats, or is an integral part of a survival craft. These devices have been phased out by the FCC and may no longer be used, marketed or sold in the U.S..
Category I
406/121.5 MHZ. Float-free, automatically activated EPIRB. Detectable by satellite anywhere in the world. Recognized by GMDSS.
Category II
406/121.5 MHZ. Similar to Category I, except is manually activated. Some models are also water activated.
Inmarsat E
1646 MHZ. Float-free, automatically activated EPIRB. Detectable by Inmarsat geostationary satellite. Recognized by GMDSS. These devices have been phased out by Inmarsat.
121.5/243 MHz EPIRBs
The International Cospas-Sarsat System ceased satellite processing of 121.5/243 MHz beacons on 1 February 2009. Although Emergency Locator Transmitters used by aircraft may still be used, alerts from these devices or from 121.5/243 MHz EPIRBs will no longer be acted upon unless detected by an overflying aircraft.
Make sure you get a new 406MHz EPIRB. Preferable one with built-in GPS so the coordinates are immediately transmitted. Ones without GPS require multi-satellite triangulation and won't pinpoint your position nearly as accurately as GPS units.
