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Subelement C
Satellite Systems:
Section 30
Equipment Faults and troubleshooting-1:
Which of the following conditions would prevent communications between an Inmarsat-C data port and external data terminal equipment (DTE)?
  • Use of a stop bit in the DCE/DTE communication parameters.
  • Grounding pin 5 of the standard EIA-232 connector.
  • Use of a "0" parity bit in the DCE/DTE communication parameters.
  • Correct Answer
    Use of a "null" MODEM cable to connect the DTE device.
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How can a LES/RCC (Rescue Coordination Centre) determine if an Inmarsat-C Distress Alert is a TEST transmission?
  • Correct Answer
    A flag in the message is set to identify the transmission as a test alert.
  • The validity of each Distress alert must be manually verified by LES/RCC personnel.
  • A Distress acknowledgement is sent from the LES/RCC to the originating station.
  • LES/RCC personnel cannot distinguish between valid and TEST transmissions.
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What is the meaning of the "ACB" Inmarsat-C Non-Delivery Notification (NDN) failure code?
  • The terminal received an invalid answer-back from the destination.
  • Correct Answer
    Access to the Inmarsat system has been barred.
  • The Automatic Communications Bit error rate was exceeded.
  • An Inmarsat message channel failure occurred.
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What condition can indicate a communication failure between the second receiver (RX2) and the Antenna Control Unit (ACU) in an Inmarsat Fleet 77 terminal?
  • The terminal will indicate RX2 is locked onto a signal on the Inmarsat NCSC channel.
  • The terminal will indicate receipt of a valid frame on the Inmarsat NCSC channel.
  • Correct Answer
    The message "RX2 Comm error" or "ACU Comm error" will be displayed.
  • The DCE/DTE communication protocol is improperly configured.
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Which of the following devices can cause interference to Fleet 77/55 systems?
  • 406 MHz Emergency Position Indicating Radio Beacons (EPIRBs) in the transmit mode.
  • 9.3 GHz Search And Rescue RADAR Transponders (SARTs) in the transmit mode.
  • Correct Answer
    Transmitters operating in the 3-30 MHz range and shipboard RADARS in close proximity.
  • Survival Craft Equipment in the VHF range in the high power transmit mode.
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What error message may be displayed if a connection to the Inmarsat Mobile Packet Data Service (MPDS) network fails?
  • "ECM 0071" is displayed indicating the called station ID was not properly decoded.
  • "ECM 00F0" is displayed indicating the terminal's failure to transmit over the Inmarsat network.
  • "77F0h" or "77F1h" is displayed indicating the terminal is not registered to the MPDS network.
  • Correct Answer
    "00F0h" or "00F1h" is displayed indicating the terminal is not registered to the MPDS network.
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