Why Your Old Man Overboard Beacon Might Not Cut It Anymore

Falling overboard is every mariner’s worst nightmare, a chaotic event where seconds count. We invest in high-quality gear because we believe in that layer of protection. But the technical landscape is shifting, and what worked perfectly a few years ago might soon provide a false sense of security.

If you’re still relying on older Man Overboard (MOB) beacons that are strictly AIS (Automatic Identification System), it’s time to talk about Class M compliance and why the entire industry is pivoting.

The Problem with AIS-Only Beacons

Traditional AIS MOB beacons are ingenious devices. When activated, they transmit your GPS position as an AIS target directly to chart plotters on all vessels within VHF range. This puts a flashing symbol on a screen, showing exactly where you are. They are visual locators, designed to guide a rescue team directly to you.

But as useful as this is, there is a fundamental drawback. These beacons silently call for help.

They rely on someone aboard a nearby vessel actively monitoring their AIS screen, understanding the emergency, and responding quickly. In a fast-moving emergency, or on a short-handed bridge, a silent blip on a screen can be overlooked, leading to fatal delays.

Furthermore, maritime regulations are changing to address the congestion on standard AIS channels (161.975 MHz). To reduce channel clutter from commercial shipping, authorities are pushing non-compliant, non-voice distress devices (like older AIS MOB beacons) onto less-monitored frequencies. In many regions, the use of these older AIS beacons on primary channels will be strictly prohibited by early 2025. This move significantly reduces their likelihood of being noticed by immediate nearby rescue assets, making them less effective as a primary emergency system.

The Sentinel MOB Journey (Transparency and Future-Proofing)

At Sentinel Ocean Systems (SOS), our mission is simple: to keep you safe at sea. We pride ourselves on building rugged, reliable marine safety equipment. Our current flagship MOB beacons are highly engineered AIS devices, excellent at what they are designed to do. However, to meet this new global standard and provide the most robust alerting capability, they must integrate Digital Selective Calling (DSC).

We need to be clear: our existing MOB beacons are not yet Class M compliant. This means that while they still provide highly accurate AIS positioning on secondary channels, they do not offer the audible, unignorable alert required by the new standard and cannot participate in the global DSC system for human distress.

We understand that you expect the latest technology from a premium safety brand, and we want to assure you that the entire SOS team is dedicated to meeting this new challenge.

The Sentinel Class M Solution (Coming Later This Year)

We aren’t just identifying the problem; we are building the solution. SOS is in advanced development on new releases of our MOB products that will be fully Class M compliant. These devices, launching later this year, will redefine what’s possible in personal maritime safety.

What will this new technology offer?

Integrated DSC (Unignorable Audio Alarm)

Class M compliant devices combine AIS visual tracking with DSC technology. Upon activation, the beacon will broadcast a localized, high-priority DSC distress alert on VHF Channel 70. This alert triggers an automated, piercing audible alarm on the VHF radios of every vessel within range, forcing a critical immediate response.

Two-Way Acknowledgment

The new Sentinel Class M beacons will support Two-Way Acknowledgment (TWA). This allows a nearby vessel or Coast Guard station to send an acknowledgment signal back to your beacon once your DSC distress call is received. The beacon can then communicate this confirmation to you and automatically mute its audible radio alarms, clearing the airwaves for clear communication while the AIS visual target continues to broadcast your exact location to rescue crews.

Gear Up for Reality

The ocean is unforgiving and does not care about old equipment. If you operate in high-risk marine environments, you cannot afford to cut corners. Upgrading to a modern AIS/DSC MOB beacon ensures that if the worst happens, you are not just seen on a screen, but you are also heard and responded to.

We are committed to providing you with the gear that provides the ultimate chance of a fast rescue. Watch this space, and sign up for our SOS newsletter to be the first to know when the new Class M compliant Sentinel beacons are ready to keep you and your crew safe.