How to send a DSC distress alert

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Lift the cover over the red DISTRESS button and press and hold it until the radio confirms the alert has gone, usually more than 3 seconds. Then, once the alert is acknowledged or after about 15 seconds, give your MAYDAY call by voice on VHF channel 16.
When to call: Press the DSC distress button only when a vessel or person is in grave and imminent danger and needs immediate help (a MAYDAY situation); for an urgent problem with no immediate danger to life, make a PAN-PAN call on channel 16 instead. Who answers where you are →

Step by step

  1. Use it only for grave and imminent danger

    The DSC distress alert is the digital form of MAYDAY. Use it when there is grave and imminent danger and you need help now.[1]

  2. Lift the cover and hold the red button

    Lift the cover over the red DISTRESS button and press and hold it until the alarm and light go steady and the alert is sent, which usually takes more than 3 seconds.[5][2][16]

  3. Add the nature of distress if there's time

    If you have time, many radios let you choose the type of emergency from a menu before sending. If not, just send the alert.[13]

  4. Check your position is included

    The alert only carries your position if the radio has its own GPS or is connected to one. If it doesn't, you must give your position by voice.[8][6]

  5. Follow up with MAYDAY on channel 16

    Once the alert is acknowledged, or after about 15 seconds, call on channel 16: "MAYDAY, MAYDAY, MAYDAY, this is [boat name ×3], [call sign], [MMSI]. MAYDAY [boat name, call sign, MMSI]. Position… Nature of distress… Help needed… Number of people on board… Over."[3][6][9]

  6. Expect an acknowledgement

    If you are in range, the coastguard should acknowledge your alert digitally. Until it is acknowledged or you stop it, the radio repeats the alert automatically about every 4 minutes.[9][14]

  7. Stay by the radio

    Stay by the radio and keep listening on channel 16. Rescuers can find you faster if you keep in contact.[24]

  8. Use your EPIRB or PLB as well

    If you carry an EPIRB, it is your second means of raising the alarm.[7]

  9. Pressed it by mistake? Cancel at once

    Cancel the alert straight away using your radio's cancel option, then tell all stations on channel 16 your boat name, MMSI and that you are cancelling a false alert, with the time it was sent. You won't normally get into trouble if you cancel promptly.[11][22][12][23]

  10. Know your range

    VHF range depends on antenna height. A handheld radio or a low antenna covers a smaller area, and DSC coastguard coverage varies from place to place.[4][20]

Don't

Before you sail

Frequently asked

What happens after I press the DSC distress button?

Your radio sends a digital alert with your MMSI and, if connected to GPS, your position to all DSC radios and coast stations in range. It repeats about every 4 minutes until acknowledged. Follow it with a voice MAYDAY on channel 16.

Do I still need to make a MAYDAY call after a DSC alert?

Yes. After the acknowledgement, or about 15 seconds, give your full MAYDAY message by voice on channel 16.

What do I do if I sent a DSC distress alert by mistake?

Cancel it immediately and announce the cancellation on channel 16 with your boat name and MMSI. Sources differ on one detail: the US Coast Guard says not to switch the radio off before cancelling, while Transport Canada and the older IMO-based procedure say to switch off and on. Check your radio's manual.

Why does my DSC radio need an MMSI?

The MMSI is your boat's 9-digit identity. It is programmed into the radio and tells rescuers who is sending the alert.

Will a DSC alert send my position?

Only if the radio has built-in GPS or is connected to a GPS. Otherwise, give your position by voice in your MAYDAY call.

Sources

  1. Maritime and Coastguard Agency (HM Coastguard) (2026-10-14): “Only to be used in the event of grave and imminent danger and assistance is required.”
  2. Maritime and Coastguard Agency (HM Coastguard) (2026-10-14): “press and hold the button until the alert is sent”
  3. Maritime and Coastguard Agency (HM Coastguard) (2026-10-14): “On receipt of a DSC acknowledgement or after about 15 seconds, transmit the distress call and message on Channel 16”
  4. Maritime and Coastguard Agency (HM Coastguard) (2026-10-14): “This area relates to a vessel with an antenna 4m above sea level. Where the antenna is lower or it is a portable radio, the area is smaller.”
  5. IMO – Guidance on distress alerts (MSC.1/Circ.1658) (2026-10-14): “LIFT COVER PRESS RED BUTTON until acoustic and light-indication becomes steady (more than 3 seconds)”
  6. IMO – Guidance on distress alerts (MSC.1/Circ.1658) (2026-10-14): “POSITION Given as latitude and longitude or If latitude and longitude are not known or if the time is insufficient, in relation to a known geographical location”
  7. IMO – Guidance on distress alerts (MSC.1/Circ.1658) (2026-10-14): “Do not forget, your EPIRB is the secondary means of alerting”
  8. US Coast Guard Navigation Center (2026-10-14): “DSC distress alerts include position information, but only if the radio has an internal GPS or is connected to a GPS.”
  9. US Coast Guard Navigation Center (2026-10-14): “Once the distress alert is transmitted, contact the Coast Guard on VHF channel 16 and communicate your distress information. The Coast Guard will digitally acknowledge your distress alert if you are in VHF range.”
  10. US Coast Guard Navigation Center (2026-10-14): “DO NOT power off the radio before cancelling the alert. Otherwise, most radios will continue transmitting the alert once it is powered up again.”
  11. US Coast Guard Navigation Center (2026-10-14): “All DSC-equipped radios have a menu selection for cancelling a distress call once distress is activated. Transmit that cancellation. Then notify ships and the Coast Guard of the cancelation, your MMSI and the name of your boat on channel 16”
  12. US Coast Guard Navigation Center (2026-10-14): “You won’t get into trouble by accidentally sending a DSC distress alert if you cancel it immediately.”
  13. US Coast Guard (Drill Down No. 21: DSC Distress Alerting) (2026-10-14): “If time permits, there are additional menu options for the operator to select and format the distress alert with more information regarding the nature of the distress.”
  14. US Coast Guard (Drill Down No. 21: DSC Distress Alerting) (2026-10-14): “Once initiated, a DSC distress alert on VHF will be repeated automatically at intervals of about 4 minutes until it is either acknowledged by another station or stopped manually.”
  15. US Coast Guard (Drill Down No. 21: DSC Distress Alerting) (2026-10-14): “The identity of the vessel is by a nine-digit Maritime Mobile Service Identity (MMSI) number issued by the FCC, programmed into the DSC equipment”
  16. Transport Canada – Safe Boating Guide (TP 511E) (2026-10-14): “If your VHF radio has Digital Selective Calling (DSC) on channel 70, press the button to send a digital distress call.”
  17. Transport Canada – Safe Boating Guide (TP 511E) (2026-10-14): “Follow the specific instructions for canceling DSC distress calls in your DSC owner’s manual. This includes: • switching the unit off and on • select channel 16 • broadcasting the boat name and your MMSI number”
  18. Transport Canada – Safe Boating Guide (TP 511E) (2026-10-14): “VHF channel 70 is only used for DSC (digital) communication. Voice communication is not allowed”
  19. Transport Canada – Safe Boating Guide (TP 511E) (2026-10-14): “A Maritime Mobile Service Identity (MMSI) is a 9-digit number, that identifies your vessel or boat.”
  20. Transport Canada – Safe Boating Guide (TP 511E) (2026-10-14): “VHF/DSC radios can send distress alerts to the Canadian Coast Guard MCTS and nearby vessels to let them know you need help right away. Find out where VHF/DSC service is available”
  21. Transport Canada – Safe Boating Guide (TP 511E) (2026-10-14): “It’s also a good idea to keep a laminated script close to your VHF radio.”
  22. US Coast Guard Navigation Center (IMO false-alert procedure) (2026-10-14): “switch equipment on and set to Channel 16; and make broadcast to "All Stations" giving the ship's name, call sign and DSC number, and cancel the false distress alert.”
  23. US Coast Guard Navigation Center (IMO false-alert procedure) (2026-10-14): “No action will normally be taken against any ship or mariner for reporting and cancelling a false distress alert.”
  24. US Coast Guard Navigation Center (2026-10-14): “Stay by the radio if possible. Even after the message has been received, the Coast Guard can find you more quickly if you can transmit a signal on which a rescue boat or aircraft can home.”

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Rescue numbers by country → How to make a MAYDAY call → Printable emergency card →

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