Module 8 - Digital Selective Calling
Routine Individual DSC Calls
What you will learn
Complete the different routine DSC workflows for a known vessel and a coast station without speaking on Channel 70 or assuming a channel was accepted.
A routine DSC call rings one known station. Inter-ship calls propose a suitable inter-ship channel; a coast station returns the voice channel it wants used.
For a known vessel, select or enter its verified MMSI, choose an individual call with routine priority and indicate a suitable inter-ship radiotelephony channel. Send the call and wait. When the called vessel acknowledges, the voice conversation can start on the selected channel.
For HM Coastguard or another DSC-equipped coast station, make an individual routine call to the correct coast-station MMSI. The coast station's acknowledgement indicates the working voice channel. Tune to that channel and wait for the coast station to call you; do not begin an extended voice call on Channel 16 or Channel 70.
If the other vessel's MMSI is unknown, the current MCA small-craft route is a voice call on Channel 16, initially at low power, then move to an inter-ship channel once contact is made. The bounded Channel 13 fallback applies only after no response in that inter-ship case; it is not a general routine calling channel.
Worked example
Fictional yacht Compass Rose wants a short routine exchange with a known yacht using inter-ship Channel 72.
- 1Verify the called yacht's nine-digit MMSI and that Channel 72 is suitable for the intended inter-ship traffic.
- 2Select Individual, Routine, the verified MMSI and Channel 72; review the display, then send.
- 3Wait for the digital acknowledgement. Confirm that the set is on the accepted Channel 72.
- 4Call the yacht by voice, identify Compass Rose and conduct the concise exchange. End OUT when no reply is required.
Sense check: No voice is transmitted on Channel 70, and a transmit indication is not treated as an acknowledgement.
| Target | DSC selection | Voice channel decision |
|---|---|---|
| Known vessel | Individual, routine, verified MMSI | Caller proposes a suitable inter-ship channel |
| Coast station | Individual, routine, current station MMSI | Station returns the working channel |
| Unknown vessel MMSI | No guessed DSC address | Voice Channel 16, then move after contact |
Wait for the accepted route
A coast-station DSC acknowledgement returns a working channel different from the one the operator expected.
1. Read the response
Confirm the acknowledging identity and the working channel shown by the set.
2. Tune deliberately
Set the returned channel rather than continuing on the calling channel.
3. Wait for the call
Allow the coast station to initiate the voice exchange on its indicated channel.
Sense check: The digital acknowledgement is the evidence for the next channel; habit or expectation is not.
Common mistake or limitation
- Speaking before a digital acknowledgement and channel agreement.
- Using an unverified MMSI because a vessel name looks familiar.
- Treating Channel 13 as a general alternative to routine DSC or Channel 16.
Recap
- Known vessel: individual routine DSC and a suitable proposed inter-ship channel.
- Coast station: accept its returned channel and wait for its voice call.
- Unknown MMSI: use the published voice route rather than guessing an identity.
Optional quick check
Section 7 of 9
After a coast station acknowledges a routine DSC call and returns a working channel, what should the yacht do?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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