A1
Sea area A1 means an area within the radiotelephone coverage of at least one VHF coast station in which continuous DSC alerting is available, as may be defined by a Contracting Government.

A2
Sea area A2 means an area, excluding sea area A1, within the radiotelephone coverage of at least one MF coast station in which continuous DSC alerting is available, as may be defined by a Contracting Government.

A3
Sea area A3 means an area, excluding sea areas A1 and A2, within the coverage of a recognized mobile satellite service supported by the ship earth station carried on board in which continuous alerting is available.

A4
Sea area A4 means an area outside of sea areas A1, A2 and A3.

AIS SART
AIS-SART (Automatic Identification System - Search And Rescue Transmitter) is a device that transmits a position-related distress message based on the Automatic Identification System (AIS) protocol. The position and time synchronization of the AIS-SART is carried out via a built-in GPS module

DSC
Digital selective calling (DSC) means a technique using digital codes which enables a radio station to establish contact with, and transfer information to, another station or group of stations, and Radio Consultative Committee (CCIR).

EPIRB
Emergency Position Indicating Radio Beacon: tracking transmitter which aid in the detection and location of boats, aircraft, and people in distress.

GNSS
Global Navigation Satellite System

GMDSS
Global Maritime Distress and Safety Radio System

GPS
Global Positioning System

GT
Gross tonnage

HF
High Frequencies (HF) designated for marine communication range between 4000 kHz to 27500 kHz and are called "u" band. This is divided into the following sub-bands: 4, 6, 8, 12, 16, 18/19, 22, 25/26 MHz. Only the first five are used for distress and safety communication.

LEO
When the satellite is moving in a low earth orbit, for example at an altitude of 200 to 2000 kilometers.

MF
Medium Frequencies (MF) designated for marine communication range between 1605 kHz to 3800 kHz and are called "t" band.

MSI
Maritime Safety Information - Navigational and meteorological warnings, meteorological forecasts, and other urgent safety-related information broadcast to ships.

NAVTEX
Information system for receiving maritime safety information on the 518 kHz (Englisch), 490 kHz (local language) and 4209.5 kHz.

RMSS
Recognized Mobile Satellite Service

SAR
Search And Rescue

SART
Search And Rescue Transponder

SBM
Shore based maintenance

SES
Ship Earth Station

SOLAS
Safety of life at sea

VHF
Maritime Radio: refers to the radio frequency range between 156.0 and 162.025 MHz, inclusive. In the official language of the International Telecommunication Union (ITU) the band is called the VHF maritime mobile band.