further allowing this data to be presented directly on an Electronic Chart Display and Information System (ECDIS). This presents a significant improvement over the text-only NAVTEX system. As of February 2023, no maritime authorities have begun NAVDAT broadcasts. Amateur radio Maritime traffic currently displaced from the 500 kHz band in most countries, and with the ITU 472–479 kHz amateur allocation, most countries no longer using it have allocate frequencies near 500 kHz to amateur radio use on a secondary basis, although the primary allocation of the band remains with the maritime mobile service. Full details of these allocations can be found under the article on the 630 metre amateur radio band. See also 2182 kHz the international distress frequency for voice maritime communication 630-meter band Navtex a maritime weather and safety text broadcast on 518 kHz and 490 kHz Aircraft emergency frequency Call for help for emergency frequencies in current use Distress signal GMDSS Mayday Medium frequency radio propagation Radio Act of 1912 Radio propagation SOS References External links — (Includes the 1912 London Radiotelegraphic Convention) Maritime communication History of radio Emergency communication Morse code