Survival radio

This frequency had the advantage of long range due to ground-wave propagation and was constantly monitored by all large ships at sea after the Titanic's sinking.

During World War II, Germany developed a hand-crank 500 kHz rescue radio, the "Notsender" (emergency transmitter) NS2.

The radio case curved inward in the middle so that a user seated in an inflatable life boat could hold it stationary, between the thighs, while the generator handle was turned.

Nicknamed the Gibson Girl because of its hourglass shape, it was supplied with a fold-up metal frame box kite, and a balloon with a small hydrogen generator, for which the flying line was the aerial wire.

A post-World War II version, the AN/CRT-3, which added a frequency in the 8 MHz range, was in use by ships and civil aircraft until the mid-1970s.

[citation needed] After a light plane with two U.S. congressmen on board went down in 1972 and could not be found,[7] the U.S. began requiring all aircraft to carry an Emergency Locator Transmitter (ELT) that would turn on automatically in the event of a crash.

These are being phased out in favor of ELTs that use a 406.025 MHz signal, which can be picked up by the Cospas-Sarsat international satellite system for search and rescue.

Users are required to register the code with the Cospas-Sarsat, allowing inquiries to be made when a distress signal is picked up.

Maritime practice has shifted from rescue radios on 500 kHz distress frequency (which is no longer officially monitored) to the Global Maritime Distress Safety System, which includes use of the Cospas-Sarsat system and other measures, including radar transponders and hand-held marine VHF radios.