| Once
activated, both of the radios start transmitting. 24,000 or so
miles up in space, a GOES weather satellite in a geosynchronous
orbit can detect the 406 MHz signal. Embedded in the signal is a
unique serial number and, if the unit is equipped with a GPS
receiver, the exact location of the radio. If the EPIRB is
properly registered, the serial number lets the CoastGuard know
who owns the EPIRB. Rescuers in planes or boats can home in on the
EPIRB using either the 406 MHz or 121.5 MHz signal.
Older EPIRBs did not contain the
GPS, so the GOES satellite received only a serial number. To
locate the EPIRB, another set of satellites (like the TIROS-N
satellite) orbiting the planet in a low polar orbit could pick up
the signal as it passed overhead. This would give a rough fix on
the location, but it took several hours for a satellite to come
into range.
Information
courtesy of http://www.howstuffworks.com |
