If the vessel is beyond range of NAVTEX...

🔍 Key Concepts

• GMDSS MSI (Maritime Safety Information) coverage areas: NAVTEX vs. SafetyNET (Inmarsat-C) vs. HF NBDP (Narrow Band Direct Printing) • Difference between ARQ (Automatic Repeat reQuest) and FEC (Forward Error Correction) telex modes for broadcast vs. two-way traffic • Which frequencies and modes are actually used for HF MSI broadcasts under GMDSS when outside NAVTEX and Inmarsat coverage

💭 Think About

• Ask yourself: when you are beyond NAVTEX range and your Inmarsat-C (SafetyNET) receiver is down, what other GMDSS subsystem is specifically intended to receive MSI over long range? • Is MSI to many ships at once usually sent using a two-way (ARQ) mode or a one-way broadcast (FEC) mode, and on what bands (MF vs HF) for ocean areas? • Look at the options that mention 518 kHz and consider: is 518 kHz primarily associated with NAVTEX or with HF MSI NBDP broadcasts?

✅ Before You Answer

• Verify which mode (FEC vs ARQ) is specified in GMDSS for MSI broadcast over MF/HF NBDP. • Check whether 518 kHz is a NAVTEX frequency or an HF MSI NBDP frequency. • Confirm that when outside both NAVTEX and Inmarsat-C coverage, MSI is obtained on designated HF MSI frequencies using FEC NBDP, not by waiting without any MSI.

If the vessel is beyond range of NAVTEX broadcasts and the Inmarsat-C system fails, the GMDSS operator must:

Select 518 kHz ARQ TELEX on the MF/HF console to receive MSI.

Request repairs of the Sat-C system and wait until within range of NAVTEX.

Select 518 kHz FEC TELEX on the MF/HF console to receive MSI.

Select an HF MSI frequency and FEC TELEX mode to receive MSI.

🔍 Key Concepts

💭 Think About

✅ Before You Answer