What does “DISTRESS” signal mean?

Distress signal :-

The distress signal mayday indicates that a ship, aircraft or other vehicle is threatened by grave or imminent danger and require immediate assistance.

Distress alert :-

The transmission  of distress alert in GMDSS indicate a ship or aircraft or any other vehicle or other person is threatened by grave and imminent and requires immediate assistance.

The Radio telephone distress procedure consist of :-

1. The alarm signal (whenever possible) followed by
2. The distress call
3. The distress message with full implementation of GMDSS in Feb 1999.

The automatic alarm device used on 2182 Khz are no longer required.

FORMAT of RADIO Telephony distress call :-

Mayday (x3)
This is
Name (x3) / Call sign / MMSI no. of ship.
Radiotelephony distress message
Mayday
Name/ Call sign/ MMSI
Position
Nature of distress .

Type of assistance required any other information which might facilitate the rescue.

Format of NBDP distress call and message

MAYDAY
DE
CALL Sign
MAYDAY
Name/ Call Sign
Position
Nature of distress
Type of distress/ assistance required
Additional information that may facilitate rescue.
MASTER
NAME/ Call sign
Time (UTC)
NNNN