Just a comment on the EPIRBs. The original type (developed to locate downed pilots during the Vietnam war) broadcasts a signal on 121.5 and 243MHz, these being the civil and military emergency frequencies respectively. All aircraft with two VHF sets (includes all airliners) normally have one tuned to this all the time (and use it for gossip), which together with high cruising altitude of pressurised airliners ensured coverage almost everywhere. When a signal is detected, the alarm is raised, and a search pattern is flown at decreasing altitudes to locate the position. Different modulation is used (or supposed to be) for Land, sea and air beacons, and some also have VHF transceivers built in.
Around twenty years ago several satellites were launched which detect these signals, and relay them to national search and rescue centres. They also allow the position to be determined using the doppler shift of the signals, but the accuracy is limited by the frequency stability of the beacon. With their proliferation in recent years, false alarms have become a major problem, and to alleviate this and to improve accuracy (and hence reduce costs of searches), a new set of satellites was launched around ten years ago. These use a higher frequency beacon with a more stable frequency, and each beacon transmits an identification code, and this is registered when it is sold (so that it is immediately clear who is missing - or responsible for the false alarm). They are also more expensive.
The old satellites will be decomissioned as mentioned, but beacons would still be detected by aircraft. Whether such signals would be acted on after satellite decomissioning is a moot point, but I'm guessing that if in a remote area they would be.
John
