GOC GMDSS Exam key terms

A transmission sent only when a ship or person faces grave and imminent danger and needs immediate help, giving identity, position and the nature of the emergency so rescue services can act.

The spoken radiotelephone signal word that announces a distress call and precedes the distress message, indicating that a vessel or person is threatened by grave and imminent danger.

The spoken radiotelephone signal word used to announce an urgent message about the safety of a ship or person, without immediate danger of loss, and to request assistance where appropriate.

The spoken radiotelephone signal word, repeated three times, that introduces a safety message containing important navigational or meteorological warning information of interest to vessels in the area.

The priority setting on a Digital Selective Calling controller that marks a call as distress, which is transmitted before all other traffic and is automatically relayed by coast stations and other ships.

The continuous automatic monitoring of the dedicated Digital Selective Calling frequencies by a radio installation, so that distress and routine calls addressed to the vessel are received without a operator being present.

A three-digit number allocated to a country that forms the leading part of a ship station identity, allowing a receiving station to determine the flag state of the vessel that sent the call.

A nine-digit Maritime Mobile Service Identity permanently programmed into a ship's radio equipment that uniquely identifies the vessel, its DSC calls, and its AIS and distress transmissions.

A sea area covered by at least one VHF coast station providing continuous Digital Selective Calling alerting, within which a ship may carry VHF equipment instead of longer-range radiocommunication installations.

A sea area outside A1 that is covered by at least one medium frequency coast station providing continuous Digital Selective Calling alerting, typically extending about 100 to 150 nautical miles offshore.

A sea area outside A1 and A2 covered by an Inmarsat geostationary satellite providing continuous alerting, roughly between 70 degrees north and 70 degrees south latitude.

The remaining sea areas outside A1, A2 and A3, including the polar regions, where no satellite or shore-based alerting coverage exists and HF radio is required for distress communications.

The nine capabilities a ship must be able to perform, including distress alerting, locating, search and rescue coordination, MSI reception, and general radiocommunication, which determine the equipment carried.

A narrow-band direct-printing service broadcasting maritime safety information in English on 518 kHz from coast stations, received automatically by a dedicated receiver that prints or stores messages for the navigator.

The Inmarsat Enhanced Group Call service that broadcasts maritime safety information to defined geographic areas, received by an Inmarsat terminal able to display or print the messages.

Navigational warnings, meteorological forecasts, search and rescue information and other urgent safety broadcasts issued to ships through NAVTEX, SafetyNET and other services to support safe navigation.

An Emergency Position-Indicating Radio Beacon that transmits a distress alert with the vessel identity and position, typically via the COSPAS-SARSAT satellite system, to alert rescue authorities after a disaster at sea.

A Search and Rescue Transponder that responds to a radar signal by transmitting a series of dots on the radar display, allowing a survivor's position to be located by searching vessels and aircraft.

A portable device that transmits an automatic identification system distress message with its position, so that nearby ships can display the survivor's location on their AIS equipment instead of a radar screen.

An international satellite system that detects and locates distress beacons operating on 406 MHz, providing alert data to rescue coordination centres so that search and rescue operations can begin quickly.

The national database record linking a distress beacon's unique identifier to the vessel, owner and emergency contacts, which allows rescue authorities to confirm an alert and contact the owner.

A satellite communications organisation providing global mobile services through geostationary satellites, supporting distress alerting, telephony, data and maritime safety information broadcasts for GMDSS-equipped ships.

Medium and high frequency radio equipment fitted with Digital Selective Calling, used for distress alerting and general communication beyond VHF range, including in sea areas A2 and A4.

The behaviour of high frequency radio waves that travel beyond line of sight by refraction in the ionosphere, with usable frequencies varying by time of day, season and distance.

A radio wave that follows the curvature of the earth along its surface, providing reliable medium and low frequency communication over relatively short distances independent of ionospheric conditions.

The maximum distance over which very high frequency radio communication is possible, limited by the horizon and extended by antenna height, typically around 20 to 30 nautical miles between ships.

A periodic check in which a reserve battery is discharged and its capacity and specific gravity or voltage measured to confirm it can supply the required load for the specified period.

A dedicated battery or emergency generator that can power the radio installation for a defined period, such as one hour for VHF or six hours for MF/HF, if the main supply fails.

The routine checks required of the radio installation each day, including DSC, radiotelephone and battery checks, with results recorded in the radio log to demonstrate that equipment is serviceable.

The official record kept on board in which distress, urgency and safety communications, watchkeeping arrangements, equipment tests and faults are entered with times and positions.

The periodic inspection and certification of a ship's radio installation by an authorised surveyor to confirm that it meets carriage requirements and is in proper working order.

The authorisation issued by a national administration that permits a vessel to operate radio equipment and assigns its identity and call sign under the maritime radio regulations.

The qualification document held by a person who has passed the required examination, showing competence to operate GMDSS radio equipment and to conduct distress, urgency and safety communications.

The ability of radio and electronic equipment to operate without causing or suffering harmful interference, achieved through antenna separation, screening and careful installation practice.

The siting, mounting and cabling of antennas so that they radiate and receive effectively while avoiding interference, including adequate separation between VHF, MF/HF and satellite antennas.

A transmission by a station other than the one in distress that passes on a distress alert or message, permitted when the distressed station cannot transmit or when a coast station has not acknowledged.

Short-range VHF radiotelephone communication between ships and with shore stations for navigational safety, typically on designated channels and distinct from public correspondence traffic.

Radio communication between a ship station and the public telephone network through a coast station, used for business and personal calls and normally charged to the vessel.

A battery-powered handheld VHF transceiver carried for use in survival craft, operating on the maritime distress and safety channels to communicate with rescue units at the scene.