Subelement B: MF-HF-DSC-SITOR (NBDP) Equip. & Operations— Topic :
Question 21B1
Element 9 (GMDSS Maintainer)If a vessel is within range of NAVTEX broadcasts and both the Inmarsat-C and the NAVTEX receiver are inoperative the GMDSS operator should:
Explanation
When the primary NAVTEX receiver is inoperative, GMDSS regulations require a secondary means of receiving Maritime Safety Information (MSI). NAVTEX broadcasts on 518 kHz. The designated backup for a failed NAVTEX receiver, particularly when within NAVTEX coverage, is to use the vessel's MF/HF radio to receive Narrow Band Direct Printing (NBDP) broadcasts on the same 518 kHz frequency. Forward Error Correction (FEC) TELEX mode is the appropriate choice for this one-way broadcast reception, as it's designed for reliable reception even with some errors, without needing a return channel.
Option B is incorrect because ARQ (Automatic Repeat Request) TELEX is a two-way, point-to-point communication protocol requiring acknowledgements, which is unsuitable for receiving one-way broadcast MSI.
Option C is incorrect because waiting for repairs or until within range is not an immediate solution for vital safety information; GMDSS mandates an active alternative.
Option D is incorrect because while HF can carry MSI, the direct backup for the 518 kHz NAVTEX is MF NBDP on the same 518 kHz frequency. Also, ARQ is the wrong mode for broadcast reception.
Related Questions
20B5 Which characters are sent by the ship station to indicate a desire to send a message via a direct connection to a shoreside TELEX subscriber?20B6 What are the characters that are transmitted to terminate a direct TELEX connection in SITOR (NBDP) operations?21B2 The sequence ARQ, FEC, SFEC best corresponds to which of the following sequences?21B3 Selective FEC communications (SFEC) are employed when:21B4 Which of the following is true of SITOR (NBDP) Mode B (FEC), in the presence of static crashes.