International distress frequency

An international distress frequency is a radio frequency that is designated for emergency communication by international agreement. For much of the 20th century, 500 kHz was the primary international distress frequency. Its use has been phased out in favor of the Global Maritime Distress Safety System. Use of some distress frequencies is permitted for calling other stations to establish contact, whereupon the stations move to another frequency. Such channels are known as international calling and distress frequencies.

Other international distress frequencies, in use as of 2008, include:


 * 2182 kHz for medium range maritime voice use.


 * 121.5 MHz as the civil aircraft emergency frequency


 * Marine VHF radio Channel 16 (156.8 MHz) for short range maritime use