When a marine radio

Marine and mobile radio telephony

The Marine Radiotelephone Service or HF ship-to-shore operates on shortwave radio frequencies, using single-sideband modulation. The usual method is that a ship calls a shore station, and the shore station's marine operator connects the caller to the public switched telephone network...

 transmission begins with "Sécurité, sécurité, sécurité" (icon;
French: sécurité), it means that what follows is important safety information. The most common use of this is by coast radio stations before the broadcast of navigational warnings and meteorological information.

It is normal practice to broadcast the Sécurité call itself on a distress and listening frequency such as VHF Channel 16

Marine VHF radio

Marine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz...

 or MF 2182 kHz

2182 kHz

The radio frequency of 2182 kHz is the international calling and distress frequency for maritime radiotelephone communications on the marine MF bands.- Transmission modes :...

, and then change frequency to a working channel for the body of the messages. An equivalent Morse Code

Morse code

Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...

 signal is TTT, with each letter sent distinctly

Although mostly used by coast radio stations, there is nothing to stop individual craft broadcasting their own Sécurité messages where appropriate, for example, a yacht

Yacht

A yacht is a recreational boat or ship. The term originated from the Dutch Jacht meaning "hunt". It was originally defined as a light fast sailing vessel used by the Dutch navy to pursue pirates and other transgressors around and into the shallow waters of the Low Countries...

 becalmed (rendered motionless for lack of wind), or any vessel adrift or unable to manoeuvre near other craft or shipping lanes.

Mayday, pan-pan, securite

Of the three distress and urgency calls, Sécurité is the least urgent, after Pan-pan

Pan-pan

In radiotelephone communications, a call of three repetitions of pan-pan is used to signify that there is an urgency on board a boat, ship, aircraft or other vehicle but that, for the time being at least, there is no immediate danger to anyone's life or to the vessel itself. This is referred to as...

 (emergency on board but no immediate danger to anyone's life or to the vessel itself), and Mayday

Mayday (distress signal)

Mayday is an emergency procedure word used internationally as a distress signal in voice procedure radio communications. It derives from the French venez m'aider, meaning "come help me"....

(grave and imminent danger to life or to the vessel, requiring immediate assistance).

Example usage

A typical format for an initial call is as follows:

Sécurité, sécurité, sécurité. All ships, all ships, all ships. This is station identifier. For a weather forecast and important navigational warnings for the such-and-such area, please tune to frequency or channel number. This is station identifier out.