You are in the mid-Atlantic, out of VHF range of any coast station. Your vessel is in distress. How do you transmit a distress alert?

A. MID-OCEAN DISTRESS — MF/HF GMDSS: In ocean areas (GMDSS Sea Area A3 — covered by Inmarsat satellite), multiple distress alerting methods are available: (1) INMARSAT-C DISTRESS ALERT: send a distress priority message via Inmarsat-C (or Inmarsat-F if fitted) — this goes directly to the relevant MRCC via satellite. Most reliable in A3 areas; (2) DSC ON MF (2187.5 kHz): if MF radio fitted (required in Sea Area A2 — 150-400nm from shore), send DSC distress on 2187.5 kHz; voice MAYDAY on 2182 kHz. MF range typically 150-300nm; (3) DSC ON HF (various distress frequencies by band): for A3 ocean areas, HF DSC on one of the distress frequencies (4207.5, 6312, 8414.5, 12577, or 16804.5 kHz). Voice distress on HF 2182 kHz or appropriate working frequency; (4) EPIRB: activate the 406 MHz EPIRB — this transmits directly to COSPAS-SARSAT satellites and is received worldwide. Essential for A3 distress. RECOMMENDED SEQUENCE: (a) Activate EPIRB; (b) Send Inmarsat-C distress priority message; (c) DSC on HF and MF; (d) Voice MAYDAY on appropriate frequency. This maximises chances of distress alert being received by SAR authorities anywhere in the world.

B. In the mid-Atlantic, transmit voice MAYDAY on VHF Ch 16. VHF signals bounce off the ionosphere at sea and can be received worldwide.

C. MF/HF distress is only available to vessels with a Radio Officer. Modern vessels without a dedicated Radio Officer cannot legally use MF/HF distress.

D. The GMDSS DSC distress button on VHF Ch 70 works globally via satellite relay. Mid-ocean VHF DSC distress will be received by Inmarsat and forwarded to MRCC.

A. DSC DISTRESS ALERT — VHF PROCEDURE: DSC (Digital Selective Calling) on VHF Channel 70 is the primary GMDSS distress alerting mechanism. PROCEDURE: (1) ENSURE POSITION IS UPDATED: the DSC controller must have a current GPS position input (most modern sets auto-update from GPS). Verify the position shown is current; (2) OPEN THE DSC CONTROLLER: navigate to the distress function — typically a protected button (lift cover or press and hold to prevent accidental activation); (3) SELECT NATURE OF DISTRESS: most DSC controllers allow selection of distress nature — UNDESIGNATED, FIRE, FLOODING, COLLISION, GROUNDING, LISTING, SINKING, DISABLED AND ADRIFT, ABANDONING SHIP. If time permits, select the correct nature; (4) TRANSMIT: press/hold the distress button for the required duration (typically 5 seconds with button confirmation). The controller transmits the DSC distress call on Ch 70 — this broadcasts your MMSI, position, time, nature of distress to all vessels in range and to coast stations; (5) SWITCH TO CH 16: immediately after DSC transmission, switch VHF to Ch 16 and transmit the voice MAYDAY message; (6) MAYDAY VOICE: "MAYDAY MAYDAY MAYDAY — THIS IS [vessel name × 3] — MAYDAY [vessel name] — POSITION [lat/lon] — [NATURE OF DISTRESS] — [POB] — [ANY OTHER RELEVANT INFO] — OVER"; (7) AWAIT ACKNOWLEDGEMENT: coast stations and vessels will acknowledge on Ch 16.

B. The DSC distress alert is transmitted on Ch 16. Tune the VHF to Ch 16, press the distress button, and speak the MAYDAY message directly.

C. Voice MAYDAY on Ch 16 must be transmitted first — then the DSC alert follows. The voice call alerts nearby vessels who may not be monitoring DSC.

D. DSC distress is only for MF/HF radio. VHF uses the traditional voice MAYDAY on Ch 16 only — VHF DSC is not a required GMDSS function.

A. NAVTEX — SYSTEM AND OOW USE: NAVTEX (Navigational Telex) is an automated system that broadcasts maritime safety information (MSI) on 518 kHz (international) and 490 kHz (national language) using NBDP (Narrow Band Direct Printing). WHAT IT PROVIDES: (1) NAVIGATIONAL WARNINGS (B messages): hazards to navigation — wrecks, buoy off station, new obstructions, pilot areas, lights changed; (2) METEOROLOGICAL WARNINGS (W messages): gale warnings, storm warnings, weather bulletins; (3) PILOT SERVICE MESSAGES (P messages); (4) ICE REPORTS (I messages); (5) SAR INFORMATION (D messages): distress messages, SAR operations in the area; (6) SUBFACTS and NAVFACTS: submarine exercise areas and other military notifications. HOW IT WORKS: NAVTEX stations broadcast on a schedule. Each station has a unique letter identifier. The NAVTEX receiver is programmed to receive messages from stations covering your sea area. Messages not relevant to the vessel's area can be filtered. OOW DUTIES: (1) Ensure NAVTEX is switched on and printing; (2) Check the NAVTEX receiver is set to receive messages from stations in the current sea area; (3) READ ALL MESSAGES as they print; (4) Bring significant messages (navigational warnings, gale warnings, SAR in the area) to the master's attention; (5) CHART PLOT: plot navigational warnings on the chart/ECDIS; (6) Do NOT ignore NAVTEX messages — they contain safety-critical information.

B. NAVTEX operates on VHF Ch 68 and provides local port information for vessels within 20nm of the coast. It is only relevant when approaching port.

C. NAVTEX is a backup to weather fax and provides only meteorological information. Navigational warnings are only available through the vessel's AIS.

D. NAVTEX messages should be collected and reviewed once per watch. Urgent messages are highlighted in red and require immediate action; all others can wait.