# GMDSS GOC Revision: What to Practise With Flashcards
*2026-11-01*
VHF channel 70 carries Digital Selective Calling (DSC), so a worksheet asking for a voice conversation on it contains an error. Remembering what the letters stand for is only part of the answer. Useful **GMDSS GOC revision** also asks you to explain what a system does and spot an incorrect assumption.
This guide is for maritime radio trainees studying the **Global Maritime Distress and Safety System (GMDSS)** for the **General Operator's Certificate (GOC)**. Use its syllabus map, worked cases, and self-check alongside your course. The exercises cover concepts; equipment operation and communication drills need supervised practical training.
## Put a syllabus and a date behind the cards
The reference boundary here is **CEPT ERC/DEC/(99)01, Annex 1, amended 8 March 2024**, covering the General Operator's Certificate. The [official CEPT record](https://docdb.cept.org/document/783) identifies that version as active and links to the syllabus and national implementation information. The companion cards cover a **selected concept subset**, not every syllabus requirement or a national exam question bank.
The [Annex 1 syllabus](https://docdb.cept.org/download/4442) calls for theoretical and practical tests. Its practical and operational sections contain much more than facts to memorise. The map below identifies concepts that cards can help you recall and the related work to take into training.
| Syllabus area | Useful recall targets | Work to practise with an instructor |
| --- | --- | --- |
| A1–A3: service and system basics | Bands, sea areas, terrestrial/satellite roles | Explain the communication choices in a training case |
| B1–B4: practical skills to use a ship station | DSC, identities, NAVTEX, satellite terminology | Use equipment controls and interpret displays |
| C1–C5: selected operational procedures | Categories, MSI, alerting versus locating | Conduct communication and equipment exercises |
| D2/D4: publications and planning | Publication roles; why coverage changes along a voyage | Find and use the relevant current information |
Keep your own course checklist beside this map and leave practical requirements open until they have been assessed appropriately. Check certificate eligibility, assessments, renewal, and national requirements with the relevant administration. Finishing the deck doesn't establish readiness for a national examination.
## Ask for a function after the acronym
Start with short prompts that you can mark clearly. Then add a different question about the same concept in a later round.
| First recall question | A useful follow-up |
| --- | --- |
| What does DSC stand for? | What does it do? |
| What does MMSI stand for? | How is a standard ship-station identity structured? |
| What does MSI stand for? | Which systems deliver it? |
| What does EPIRB stand for? | How does alerting differ from locating survivors nearby? |
For DSC, a sufficient function answer is **establishing contact and transferring calling or alert information using digital codes**. The voice conversation is a separate task. For MMSI (*Maritime Mobile Service Identity*), the [ITU identification reference](https://www.itu.int/en/ITU-R/terrestrial/Pages/by-categories-faq.aspx?categorizedby=17) gives **nine digits** and the standard ship pattern **MIDXXXXXX**. MID means *Maritime Identification Digits*: these three digits identify the administration with jurisdiction over the station. Each X is a digit from 0 to 9. A coast-station pattern is **00MIDXXXX**. Use these patterns to recognise identity types; an assigned identity must come from the relevant authority.
MSI means **Maritime Safety Information**. NAVTEX receives safety broadcasts as text; satellite services also carry MSI. An EPIRB (*Emergency Position-Indicating Radio Beacon*) supplies a satellite distress alert. Radar search and rescue transponders (radar SARTs) and AIS search and rescue transmitters (AIS-SARTs) provide locating signals. The public [ITU maritime communications seminar](https://www.itu.int/wrs-24/wp-content/uploads/sites/44/2024/11/Advanced-Group_Maritime.pdf) distinguishes these functions. Equipment can serve more than one function: [SOLAS's EPIRB definition](https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.496(105).pdf) includes on-scene locating signals as well as satellite alerting.
If a card asks for an acronym's expansion, mark that answer alone. If it asks for a function, producing the expansion doesn't satisfy the prompt. The guide to [writing clearer flashcard fronts and backs](/blog/how-to-make-better-flashcards/) has more examples of keeping one retrieval target per card.
## Keep channel numbers attached to their purpose
A number without a mode is an incomplete memory. For these selected distress and safety channels, learn the pair:
| System | Digital selective calling | Radiotelephony: voice |
| --- | --- | --- |
| VHF | Channel 70: 156.525 MHz | Channel 16: 156.8 MHz |
| MF | 2187.5 kHz | 2182 kHz |
The frequency uses are set out in the [ITU Radio Regulations, 2024 edition](https://search.itu.int/history/HistoryDigitalCollectionDocLibrary/1.49.48.en.101.pdf), articles 31 and 52, and the channel/mode distinctions in [SOLAS IV/7 and IV/9](https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.496(105).pdf). The table is a recall reference, not a call sequence or a complete frequency plan.
A practice prompt can say: “A worksheet puts a spoken message on channel 70. Identify the error.” The required explanation is **channel 70 is assigned to DSC; it isn't a voice channel**. No button sequence is needed to answer that conceptual question.
## Work through three distinctions before testing yourself
### A3 follows the carried satellite service
The modernised sea-area definitions took effect on **1 January 2024**. Start with the exclusions: A1 is defined by VHF coast-station voice coverage with continuous DSC alerting; A2 uses MF coast-station voice coverage with continuous DSC alerting, outside A1. Those areas are defined by Contracting Governments.
Outside A1 and A2, A3 depends on coverage with continuous alerting from the recognised mobile satellite service supported by the ship earth station aboard. Here, *recognised* means recognised by IMO for GMDSS use. A4 is outside A1, A2, and that ship's A3. See [SOLAS IV/2.1.13 and IV/2.1.15–18](https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.496(105).pdf).
**Paper case:** Two ships share a position outside A1/A2 but carry earth stations supporting different recognised satellite services. Must their A3 coverage be identical?
**Worked answer:** Their coverage needn't match. Compare the recognised service supported by each carried station. The shared position alone doesn't settle the question. A fixed latitude rule or an assumption that every satellite terminal provides the same coverage misses that dependency.
### Receiving NAVTEX doesn't establish relevance
**Paper case:** A receiver picks up a NAVTEX transmission clearly. A trainee concludes that every warning received concerns the ship's position. What has been confused?
**Worked answer:** The trainee has treated signal reception as proof of geographic relevance. Radio coverage describes where the signal can be received; a defined service area concerns the transmitter's information service. The [Canadian Coast Guard's 2026 NAVTEX explanation](https://www.canada.ca/en/canadian-coast-guard/corporate/publications/radio-aids-marine-navigation/general.html#432) distinguishes these areas. For each training message, check its content against the ship's position and intended voyage using the relevant current publications. Clear reception alone doesn't answer that question.
A related recall task is to distinguish subject codes: **A** identifies navigational warnings, **B** meteorological warnings, and **E** meteorological forecasts. Keep the code question separate from the question about where a message applies.
### An RLS indication has a limited meaning
**Paper case:** A beacon training display shows a Return Link Service indication. Someone says, “That means a rescue vessel is already on its way.” Does the indication support that conclusion?
**Worked answer:** The indication confirms that the Cospas-Sarsat system received and localised the alert and forwarded it to the authorities. It doesn't confirm that a rescue has been organised or launched. An arrival time cannot be inferred from it either. [NOAA's RLS explanation](https://www.sarsat.noaa.gov/emergency-406-beacons/) states the distinction between alert delivery and a rescue response.
This is a useful card because it tests an inference, not another acronym. Keep the task on paper or in the approved training environment. Ordinary beacon activation can create a real alert and divert rescue resources; practical testing belongs under the manufacturer's instructions and your training arrangements.
## Try six mixed questions
One further concept matters for the HF question: long-distance HF skywave communication uses the ionosphere. Space-weather disturbances can change ionospheric conditions and degrade or disrupt propagation, as [Natural Resources Canada explains](https://www.spaceweather.gc.ca/data-donnee/ionosphere/index-en.php). That is a propagation explanation, not a diagnosis of every unreliable link.
Hide the answers and respond in a sentence or a short expression. These are original concept exercises, not official examination questions. Explain the distinction when a question asks for one; recognising the topic isn't enough to mark it correct.
1. A standard ship-station MMSI is shown as **MIDXXXXXX**. What does MID identify, and how many digits are in the whole identity?
2. A training worksheet describes a voice conversation on VHF channel 70. What needs correcting?
3. You know that a NAVTEX message's subject code is **B**. Is it a meteorological warning or a meteorological forecast?
4. An HF training link becomes unreliable during disturbed space weather. Which part of the propagation explanation should you recall?
5. A beacon's RLS indication appears. What claim about the rescue response remains unsupported?
6. You can explain DSC accurately from memory but haven't used the training station's controls. What evidence of practical skill is still missing?
### Answers and explanations
1. **MID identifies the responsible administration; the whole MMSI has nine digits.** The standard ship pattern contains three MID digits and six further digits. It doesn't make the MID a unique ship identifier on its own. See the [ITU MMSI patterns](https://www.itu.int/en/ITU-R/terrestrial/Pages/by-categories-faq.aspx?categorizedby=17).
2. **Channel 70 carries DSC, not voice.** The correction is about communication mode; this prompt doesn't ask you to conduct a call.
3. **Meteorological warning.** In this NAVTEX subject-code distinction, **E** denotes a meteorological forecast. Those categories aren't interchangeable.
4. **The ionosphere can be disturbed, degrading or disrupting HF propagation.** The [Natural Resources Canada explanation](https://www.spaceweather.gc.ca/data-donnee/ionosphere/index-en.php) connects long-distance HF communication with ionospheric conditions. This answer doesn't diagnose an actual equipment fault.
5. **RLS doesn't establish that rescue units have been dispatched or give an arrival time.** Alert receipt and forwarding are different from the resulting rescue action.
6. **Observed equipment use is still missing.** Recall of a definition doesn't demonstrate operation. Practise that skill with the instructor and training equipment, then use cards for any underlying concepts you couldn't explain.
Use the kind of error to choose the next task. Confusing B with E calls for another narrow recall prompt. Missing the HF explanation calls for rereading the concept and explaining it in your own words before more repetitions. The sixth answer calls for observed practical work with an instructor. Keep that task on your course checklist even if all your written answers are correct.
## Use spaced review alongside the rest of the course
Try to produce each answer before revealing it, check it, and correct errors. Return to difficult concepts in later sessions and mix topics so neighbouring cards don't supply the answer. A manageable session might include a few due cards and one paper case; adjust the amount to what you can explain accurately.
Research on [retrieval practice](https://www.psychologicalscience.org/journals/psychological-science/j.1467-9280.2006.01693.x/) and [spacing](https://www.psychologicalscience.org/journals/psychological-science/j.1467-9280.2008.02209.x/) supports recalling information and spreading review over time. It doesn't establish one universal interval schedule, validate these particular exercises, or show that flashcard success transfers to safe radio operation.
The companion [GMDSS/GOC radio concepts deck in English](/catalog/packages/gmdss-goc-radio-concepts/) contains 80 original cards on terminology, selected channel uses, identities, MSI, and alerting distinctions, including short reasoning prompts. It excludes full emergency scripts, acknowledgement/relay/cancellation sequences, live testing, national certification rules, and complete syllabus coverage. You can use the questions on this page without the deck; all answers are here.
Take the remaining skills into your approved course: equipment operation, spoken communication, receiving and handling calls, false-alert cancellation, and use of current publications. Regular flashcard review can help you retain the concepts behind those tasks over time. Practical assessment is still needed; neither a review streak nor a set of correct answers establishes emergency readiness.
*How this guide was made: AI was used substantially for source research, drafting, the syllabus-to-practice map, the original exercises, and the harbour illustration. The illustration is a visual metaphor, not a photograph of an actual event or an equipment guide. Public primary sources support the factual distinctions. The exercises haven't been tested with trainees or reviewed by a human GMDSS instructor. This is independent, unofficial study material; CEPT, IMO, ITU, and certification authorities haven't endorsed it.*
**GMDSS GOC Flashcards: Radio Concepts and Terminology**
80 original English cards for maritime radio trainees: GMDSS terms, current sea\-area concepts, selected channels, identification, MSI and alerting distinctions\.
80 cards · Audience languages: English \(en\)
[Study this deck for free]()
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