As of February 1, search-and-rescue satellites will stop monitoring 121.5 MHz, one of the frequencies used by emergency locator transmitters. Although there is no FAA mandate requiring a switch to 406-MHz ELTs, operators should be aware that the international Cospas-Sarsat satellite system will cease to process 121.5-MHz signals on that date. The organization, based in Montreal, recommends ELT owners begin taking steps to replace their 121.5/243-MHz units with 406-MHz beacons as soon as possible, saying a good time to consider purchasing a 406-MHz ELT is when the battery on a 121.5/243-MHz beacon needs replacing. Typically batteries must be replaced about every five years. ICAO last July began requiring 406-MHz ELTs for international operations, but the FAA still allows carriage of 121.5-MHz units for operations inside the U.S. Distress signals from these units can still be picked up with a VHF radio.