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DSC Operations Flashcards

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  1. What does 'DSC' stand for in marine radio communications?

    Answer: Digital Selective Calling

    DSC stands for Digital Selective Calling. It is a digitally encoded signalling system that allows radio operators to send automated alerts and calls to specific stations or all stations.

  2. On which VHF channel are DSC calls transmitted?

    Answer: Channel 70

    All VHF DSC calls are transmitted and received on Channel 70 (156.525 MHz). This channel is dedicated exclusively to DSC traffic and should never be used for voice communications.

  3. What is an MMSI number and why is it important for DSC?

    Answer: A unique nine-digit Maritime Mobile Service Identity that identifies a specific vessel or coast station in the DSC system

    An MMSI (Maritime Mobile Service Identity) is a unique 9-digit number assigned to each DSC-equipped vessel or coast station. It acts like a telephone number, allowing specific calls to be made.

  4. What happens when you press the dedicated 'DISTRESS' button on a DSC VHF radio?

    Answer: It sends an automated distress alert on Channel 70 containing your MMSI, position, and nature of distress to all DSC-equipped stations

    Pressing and holding the distress button transmits a DSC distress alert on Channel 70 to all stations. The alert includes your MMSI, position (from GPS), time, and nature of distress if programmed.

  5. After sending a DSC distress alert, what should the operator do next?

    Answer: Switch to Channel 16 and broadcast a Mayday voice message to provide full details of the distress

    After the DSC alert on Ch70, the radio should switch to Channel 16 where the operator must make a full Mayday voice call providing complete details including position, nature of distress, and assistance required.

  6. How should a DSC distress alert be cancelled if it was sent accidentally?

    Answer: Cancel the alert on the radio, then broadcast a cancellation message on Channel 16 to all stations and inform the coastguard

    If a false distress alert is sent, the operator must cancel it on the radio, then broadcast a cancellation on Channel 16 to all stations explaining it was a false alert, and contact the coastguard.

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Sources & references

Exam facts on this page (fees, format, dates, passing scores) are checked against these official sources; the date is our last check. Editorial policy

  1. rya.org.uk — Score release, eligibility, fees, exam format, registration deadline, test delivery · verified Oct 2026