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Subel. D
6 questions
Subelement D

DSC & Alpha-Numeric ID:

Section 27

DSC Operations

Which of the following statements concerning DSC equipment is true?

  • The GMDSS Radio Operator is not responsible for properly selecting HF DSC guard channels because they are done automatically by the watch receiver.
  • All equipment must be type accepted by Inmarsat.
  • Correct Answer
    The vessel's navigational position must be updated, either automatically or manually, no less often than every four (4) hours.
  • The GMDSS Radio Operator is responsible for properly selecting VHF & MF DSC guard channels but the HF frequencies are done automatically by the watch receiver.

Which of the following statements concerning DSC equipment is TRUE?

(C). The vessel's navigational position must be updated, either automatically or manually, no less often than every four (4) hours.

From RECOMMENDATION ITU-R M.493-11, Digital selective-calling system for use in the maritime mobile service

"The DSC equipment may also be provided with an internal electronic position fixing device. In which case, the DSC equipment should automatically switch to the internal source if the external IEC 61162 position information is not valid or not available.
If the automatic position update is not available, a displayed and audible reminder to manually update the position should occur before the position information is 4 h old."

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What is the action that a GMDSS Radio Operator should take when a DSC Distress alert is received requesting J3E?

  • No action is necessary, as the DSC control unit will automatically switch to the SITOR (NBDP) follow-on communications frequency.
  • The Operator should immediately set continuous watch on VHF channel 70.
  • The Operator should immediately set continuous watch on the SITOR (NBDP) frequency that is associated with frequency band on which the Distress alert was received.
  • Correct Answer
    The Operator should immediately set continuous watch on the radiotelephone frequency that is associated with frequency band on which the Distress alert was received.

What is the action that a GMDSS Radio Operator should take when a DSC Distress alert is received requesting J3E?

(D). The Operator should immediately set continuous watch on the radiotelephone frequency that is associated with frequency band on which the Distress alert was received.

J Stands for a single side band, with no carrier 3 Is a single channel for analog information E Voice or sound output

47 CFR 80.1111(d) All stations which receive a distress alert transmitted by digital selective calling must immediately cease any transmission capable of interfering with distress traffic and must continue watch on the digital selective call distress calling channel until the call has been acknowledged to determine if a coast station acknowledges the call using digital selective calling.

Additionally, the station receiving the distress alert must set watch on the associated distress traffic frequency for five minutes to determine if distress traffic takes place.

From Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart W relating to § 80.1111 Distress alerting

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What does the DSC control unit do if the GMDSS Radio Operator fails to insert updated information when initiating a DSC Distress alert?

  • Correct Answer
    It will initiate the DSC Distress alert and default information will automatically be transmitted.
  • It will abort the transmission and set off an audible alarm that must be manually reset.
  • It will initiate the DSC Distress alert but, as no information will be transmitted, rescue personnel will not be able to identify the vessel, its position, or its situation.
  • It will initiate the DSC Distress alert, but any station receiving it will have to establish contact with the distressed vessel to determine its identity, position, and situation.

What does the DSC control unit do if the GMDSS Radio Operator fails to insert updated information when initiating a DSC Distress alert?

(A). It will initiate the DSC Distress alert and default information will automatically be transmitted.

From RECOMMENDATION ITU-R M.493-11, Digital selective-calling system for use in the maritime mobile service

"The DSC equipment may also be provided with an internal electronic position fixing device. In which case, the DSC equipment should automatically switch to the internal source if the external IEC 61162 position information is not valid or not available.
If the automatic position update is not available, a displayed and audible reminder to manually update the position should occur before the position information is 4 h old."

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A DSC Distress alert:

  • Must always be sent on VHF Ch-70.
  • Correct Answer
    Will always be sent on one or more of the DSC Distress frequencies.
  • Must always be sent on MF 2 MHz plus one other HF DSC frequency.
  • Must always be sent on VHF Ch-70, then 2 MHz MF then 8 MHz HF.

A DSC Distress alert:

(B). Will always be sent on one or more of the DSC Distress frequencies.

§ 80.1111 Distress alerting.
47 CFR 80.1111(b) The distress alert must be sent through a satellite either with absolute priority in general communication channels or on exclusive distress and safety frequencies or, alternatively, on the distress and safety frequencies in the MF, HF, and VHF bands using digital selective calling.

§ 80.1077 Frequencies.

VHF DSC Ch. 70 - 156.525 MHz.1
VHF Ch.16 156.8 MHz
MF Radiotelephony 2182 kHz

MF/HF DSC2: 2187.5 kHz3, 4207.5 kHz, 6312 kHz, 8414.5 kHz, 12577 kHz, and 16804.5 kHz.

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In all cases, the transmit frequency of a MF/HF console DSC Distress alert:

  • Will always go out first on 2187.5 kHz to reach nearby vessels.
  • Correct Answer
    Depends upon operator DSC Call set up entries or manufacturer’s defaults.
  • Will go out on 8 MHz and 2 MHz and one other DSC Distress frequency.
  • Will always go out first on 8414.5 kHz to ensure receipt by a coast station.

In all cases, the transmit frequency of a MF/HF console DSC Distress alert:

(B). Depends upon operator DSC Call set up entries or manufacturer's defaults.

See Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart W - Global Maritime Distress and Safety System (GMDSS)

§ 80.1077 Frequencies.
VHF DSC Ch. 70 - 156.525 MHz.1
VHF Ch.16 156.8 MHz
MF Radiotelephony 2182 kHz

MF/HF DSC2: 2187.5 kHz3, 4207.5 kHz, 6312 kHz, 8414.5 kHz, 12577 kHz, and 16804.5 kHz.

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DSC relays of Distress alerts to a coast station:

  • Should be done for all Distress alerts received aboard the ship.
  • Should be transmitted to all ships involved in Distress traffic.
  • Correct Answer
    Should be avoided; unless a DSC acknowledgement has not been heard.
  • Are the best means to provide for a retransmission of Distress communications.

DSC relays of Distress alerts by vessels:

(C). Should be avoided; unless an acknowledgement has not been heard.

47 CFR 80.1117(a) Normally, distress calls received using digital selective calling are only acknowledged using a DSC acknowledgement by a coast station.

Ships should delay any acknowledgement in order to give sufficient time for a coast station to acknowledge the call.

In cases where no acknowledgement has been heard and no distress traffic has been heard, the ship should transmit a distress alert relay to the coast station.
Upon advice from the Rescue Coordination Center, the ship may transmit a DSC acknowledgement call to stop it from being repeated.

See Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart W Global Maritime Distress and Safety System (GMDSS) § 80.1117 Procedure for receipt and acknowledgement of distress alerts.

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