The red button and what comes after it: DSC procedure

Every modern VHF set has a red button under a cover. Most owners know it means distress, and that's where the knowledge ends. The sequence between "pressed" and "found" is short, and it's worth knowing by heart.

What the button does

Per the International Maritime Organization guidance (circular MSC.1/Circ.1658), the sequence is: lift the cover, press the red button and hold it until the audible and visual alarms become continuous — more than three seconds.

The set transmits a digital distress alert on channel 70. It carries your MMSI and position — but the position only goes out if the set has its own GPS receiver or is connected to an external one. The U.S. Coast Guard directly advises buying a new set with built-in GPS.

Why the button isn't enough

A DSC alert is an alarm, not a conversation. It carries no nature of distress, no number of people, no help required.

So immediately after transmitting, pick up the mic and call on channel 16 by voice. The Coast Guard will acknowledge your digital alert if you're within VHF range, but they'll only get the details from you.

The voice message sequence, from the same IMO guidance:

• MAYDAY — MAYDAY — MAYDAY;
• THIS IS and the vessel's name three times;
• call sign or other identifier, MMSI;
• position — latitude and longitude, or if unavailable or there's no time, position relative to a known landmark;
• nature of distress;
• assistance required;
• any other useful information.

Keep the frequencies visible by the set: digital calling — channel 70 and 2187.5 kHz on medium wave, voice — channel 16 and 2182 kHz. And remember the IMO wording: an emergency radio beacon is a secondary means of alerting, not a substitute for the call.

False alert: what not to do

The most common mistake is switching off the set. Don't do that: most sets will resend the alert once powered back on.

The correct procedure, per U.S. Coast Guard guidance:

1. Do not turn off the power.
2. Find the distress call cancellation option in the set's menu and send the cancellation.
3. Announce by voice on channel 16 that the alert is cancelled, stating your MMSI and vessel name.

And separately, to ease the worry: nothing will happen to you for an accidental alert if you cancel it right away. An uncancelled alert is what launches rescuers and pulls them away from real incidents — that's the actual problem.

If an alert comes in to you

Also a short sequence:

• check the position in the received call, if present;
• monitor channel 16: it will become clear whether you can help;
• wait for the digital acknowledgment from the coast guard — it clears the alarm;
• if no acknowledgment comes, contact the nearest rescue coordination center by any available means and report that you've received it.

This also covers personal man-overboard devices: many of these also send an alert, usually with a position and over a short range.

How to drill this without keying up

Training doesn't require a single real alert.

1. Print a procedure card and mount it by the set. The IMO guidance is laid out exactly this way: cover, button, MAYDAY text, fields for vessel name, call sign and MMSI.
2. Fill in your own details on the card ahead of time. Under stress, no one recalls nine digits of an MMSI.
3. Walk through it out loud with everyone aboard: who presses, who speaks, who finds the position.
4. Check that the set knows its own MMSI and sees GPS. You'll find an empty position field either now or at the worst possible moment.

The button raises the alarm. You're found by what you say next.

Sources: International Maritime Organization, MSC.1/Circ.1658 "Guidance on Distress Alerts"; U.S. Coast Guard Navigation Center, DSC Distress section.