DSC, Channel 70, MMSI and Class D Controls
How DSC alerts, addresses and priorities work on channel 70 and how a Class D controller integrates identity, position and voice-channel transfer.
How to prepare for the Marine Radio SRC
Build from station licensing and radio controls to disciplined voice and DSC traffic, then rehearse distress, urgency, safety, false-alert and GMDSS decisions on training equipment.
Core concepts
Concept 1
DSC sends digital alerting and call information on channel 70; the follow-up radiotelephony takes place on channel 16 or an indicated working channel.
Exam cue: Confirm call category, addressee and working channel before transmitting.
Concept 2
The MMSI identifies a ship, coast station, group or licensed portable equipment and must be selected or entered accurately.
Exam cue: Read the MMSI back from the display and verify directory entries.
Concept 3
A Class D set watches channel 70 for DSC while supporting VHF voice operation and can include priority, address, category, channel, position and time in a call.
Exam cue: Treat the DSC alert as the attention and data layer, then complete the required voice procedure.
Risk pitfalls and guardrails
Speaking on channel 70 after sending or receiving a DSC call.
Guardrail: Do not present the 601-item authoring target as an official RYA paper and do not treat static study as a substitute for the recognised written and practical examination.
Selecting All Ships when an individual call is appropriate.
Guardrail: Do not present the 601-item authoring target as an official RYA paper and do not treat static study as a substitute for the recognised written and practical examination.
Assuming a DSC distress alert removes the need for a Mayday voice message when one can be sent.
Guardrail: Do not present the 601-item authoring target as an official RYA paper and do not treat static study as a substitute for the recognised written and practical examination.
Memory anchors
DSC
Digital alerting and call set-up, not the full voice conversation.
70 Is Data
Channel 70 carries DSC only.
MMSI
The digital address that identifies the selected maritime station or group.
Class D
Leisure and non-SOLAS VHF DSC controller supporting channel 70 watch and voice operation.
Alert Then Voice
Use the DSC response to move to the correct radiotelephony channel.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is the primary purpose of DSC on marine VHF?
On which channel does VHF DSC transmit?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
What is Pass Harbor?
Completely free exam prep for 247 UK exams.
- Practice questions
- Flashcards
- Study guides
- Mock exams
- No registration
- No paywall
- Start instantly
“No more expensive exam prep. Quality study tools should be accessible to everyone.”