USCG Marine Communications and GMDSS — Questions and Answers

Question 1: What is the international distress, safety, and calling frequency on VHF radio?

Channel 6
Channel 16 (Correct answer)
Channel 22A
Channel 70

Correct answer: Channel 16

VHF Channel 16 (156.8 MHz) is the international distress, safety, and calling frequency required to be monitored by all vessels at sea.

Question 2: What does GMDSS stand for?

General Maritime Defense Safety System
Global Marine Distress and Safety System
Global Maritime Distress and Safety System (Correct answer)
General Maritime Distress Safety Standards

Correct answer: Global Maritime Distress and Safety System

GMDSS stands for Global Maritime Distress and Safety System, the international radio communications framework for maritime safety established under SOLAS.

Question 3: Which EPIRB type is float-free, automatically activated, and transmits on 406 MHz via satellite?

Class A EPIRB
Class B EPIRB
Category I 406 MHz EPIRB (Correct answer)
Category II 406 MHz EPIRB

Correct answer: Category I 406 MHz EPIRB

Category I 406 MHz EPIRBs are float-free, automatically activate when submerged, and use the COSPAS-SARSAT satellite system to transmit distress signals.

Question 4: Which VHF channel is designated exclusively for Digital Selective Calling (DSC) distress alerts?

Channel 6
Channel 16
Channel 22A
Channel 70 (Correct answer)

Correct answer: Channel 70

VHF Channel 70 is reserved exclusively for Digital Selective Calling (DSC) and must not be used for voice communications.

Question 5: What is the primary purpose of a NAVTEX receiver aboard a vessel?

Transmitting vessel position to the Coast Guard
Receiving navigational warnings, weather forecasts, and urgent maritime safety information (Correct answer)
Communicating with other vessels on VHF
Automatically activating the vessel's EPIRB

Correct answer: Receiving navigational warnings, weather forecasts, and urgent maritime safety information

NAVTEX is an international automated direct-printing service that receives navigational warnings, meteorological forecasts, and urgent maritime safety information on MF frequencies.

Question 6: Which signal word indicates an urgency message in maritime radio communications?

MAYDAY
SECURITE
PAN-PAN (Correct answer)
STANDBY

Correct answer: PAN-PAN

PAN-PAN (spoken three times) is the urgency signal used when a vessel has a serious situation requiring assistance but is not in immediate life-threatening danger.

Question 7: How often must GMDSS operators test DSC equipment to ensure its readiness?

Weekly
Daily (Correct answer)
Monthly
Annually

Correct answer: Daily

GMDSS regulations require daily testing of DSC equipment to verify proper function and ensure the system is operational in an emergency.

Question 8: Which GMDSS Sea Area is defined as within VHF shore-based DSC coverage, typically within 20-30 miles of shore?

Sea Area A1 (Correct answer)
Sea Area A2
Sea Area A3
Sea Area A4

Correct answer: Sea Area A1

Sea Area A1 is defined as the area within range of VHF shore-based DSC stations, generally within 20-30 nautical miles of the coast.

Question 9: What is the function of a SART (Search and Rescue Transponder)?

Sending distress calls via satellite
Locating survival craft by responding to X-band radar pulses (Correct answer)
Communicating voice messages to rescuers
Automatically activating the vessel's AIS system

Correct answer: Locating survival craft by responding to X-band radar pulses

A SART responds to X-band (9 GHz) radar pulses from searching vessels or aircraft, displaying a series of dots on the radar screen to pinpoint the location of survivors.

Question 10: What is the primary purpose of two-way VHF portable radios required in survival craft under GMDSS?

Contacting commercial shipping for navigation updates
On-scene communications between survivors and rescue units (Correct answer)
Transmitting vessel position to satellites
Broadcasting weather information to the crew

Correct answer: On-scene communications between survivors and rescue units

Two-way VHF portable radios in survival craft are used for on-scene communications between survivors and SAR rescue units during rescue operations.

Question 11: What does the COSPAS-SARSAT system primarily do?

Provides GPS navigation for commercial vessels
Detects and locates 406 MHz emergency beacons including EPIRBs and PLBs (Correct answer)
Monitors vessel traffic in coastal waters
Controls VHF radio frequency assignments in ports

Correct answer: Detects and locates 406 MHz emergency beacons including EPIRBs and PLBs

COSPAS-SARSAT is an international satellite-based search and rescue system that detects and locates distress signals from 406 MHz emergency beacons.

Question 12: Which frequency band does NAVTEX use for international maritime safety broadcasts?

VHF (156-174 MHz)
MF (518 kHz and 490 kHz) (Correct answer)
HF (4-27.5 MHz)
UHF (300-3000 MHz)

Correct answer: MF (518 kHz and 490 kHz)

NAVTEX operates on medium frequency, primarily 518 kHz for international broadcasts in English and 490 kHz for national language broadcasts.

Question 13: What vessel identifier is automatically transmitted when a DSC distress alert is sent?

The vessel's call sign
The vessel's MMSI number (Correct answer)
The vessel's IMO number
The master's license number

Correct answer: The vessel's MMSI number

A DSC distress alert automatically transmits the vessel's unique 9-digit MMSI number along with the nature of distress and GPS position when connected.

Question 14: What is the watch-keeping requirement for VHF Channel 16 on GMDSS-equipped vessels while at sea?

Only when in port
Only during daylight hours
Continuous watch while at sea (Correct answer)
At scheduled 4-hour intervals

Correct answer: Continuous watch while at sea

GMDSS vessels must maintain continuous watch on VHF Channel 16 while at sea because it is the international distress and calling frequency.

Question 15: What is the correct sequence for initiating a voice MAYDAY distress call?

MAYDAY once, vessel name, position, nature of distress, persons aboard
MAYDAY three times, vessel name three times, MAYDAY once, position, nature of distress, persons aboard, other relevant information (Correct answer)
MAYDAY twice, vessel name, position, type of assistance required
MAYDAY once, all vessel information, then wait for acknowledgment

Correct answer: MAYDAY three times, vessel name three times, MAYDAY once, position, nature of distress, persons aboard, other relevant information

The correct MAYDAY procedure begins with 'MAYDAY MAYDAY MAYDAY,' followed by the vessel's name three times, then 'MAYDAY' once more, then position, nature of distress, number of persons, and any other pertinent information.

Question 16: Which signal word announces a safety message regarding navigational hazards or important meteorological warnings?

MAYDAY
PAN-PAN
SECURITE (Correct answer)
DANGER

Correct answer: SECURITE

SECURITE (pronounced 'say-cure-ee-tay,' spoken three times) is the safety signal used to precede announcements about navigational hazards, ice reports, or meteorological warnings.

Question 17: How many digits make up a vessel's MMSI (Maritime Mobile Service Identity) number?

6 digits
7 digits
9 digits (Correct answer)
12 digits

Correct answer: 9 digits

An MMSI is a unique 9-digit number assigned to a vessel or coast station, used in DSC and AIS systems for identification.

Question 18: Under USCG and SOLAS regulations, how often must an EPIRB battery be replaced and its hydrostatic release be serviced?

Every year
Every 2 years (Correct answer)
Every 5 years
Every 10 years

Correct answer: Every 2 years

EPIRB batteries and hydrostatic releases must be replaced or serviced every 2 years, or by the expiration date printed on the unit, whichever comes first.

Question 19: What communication systems are required for GMDSS vessels operating in Sea Area A3, beyond MF range but within INMARSAT satellite coverage?

VHF radio only
VHF and MF radio only
MF/HF radio or INMARSAT satellite communications (Correct answer)
NAVTEX and EPIRB only

Correct answer: MF/HF radio or INMARSAT satellite communications

Sea Area A3 vessels must carry MF/HF radio capable of DSC on relevant frequencies and/or INMARSAT satellite equipment to ensure distress alerting capability beyond coastal waters.

Question 20: What information must be programmed into a vessel's DSC controller before it can function properly?

The vessel's flag state and home port
The vessel's MMSI number, and ideally a GPS connection for automatic position updates (Correct answer)
The captain's name and license number
The vessel's gross tonnage and passenger capacity

Correct answer: The vessel's MMSI number, and ideally a GPS connection for automatic position updates

The vessel's MMSI number must be programmed into the DSC controller; a GPS interface should also be connected so position is automatically included in any distress alert.

Question 21: Under FCC and SOLAS regulations, which vessels are required to carry GMDSS equipment?

All recreational vessels over 16 feet in length
Ships on international voyages and certain compulsory domestic routes meeting SOLAS thresholds (Correct answer)
All vessels carrying more than 6 passengers for hire
Only naval vessels and Coast Guard cutters

Correct answer: Ships on international voyages and certain compulsory domestic routes meeting SOLAS thresholds

GMDSS requirements under SOLAS and FCC rules apply to ships on international voyages and certain domestic compulsory routes, generally cargo ships of 300 GT or more and passenger ships; recreational vessels are exempt.

USCG Marine Communications and GMDSS

What is the international distress, safety, and calling frequency on VHF radio?

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Sources & references

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dco.uscg.mil — Test delivery, registration deadline, passing score, exam information · verified Oct 2026
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