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Man Over Board Deck Button and N2K  


Tom Henderson
Active Member
Joined: 3 months ago
Posts: 3
February 17, 2019 1:02 pm  

The short form of the question is "is anyone aware of a way of using an external push button to trigger an MoB event on an N2K network?". 


The context is as follows:

I'm (sadly) having to replace my lovely Leica MX412 DGPS, as it's display is dying (one row at a time), and one of the 0183 outputs now has what looks like a stuck bit. I fear it's not long for the world. The boat is a 1989 Swan 43, based on the UK's south coast. The rest of my electronics is a very complete B&G H2000 Hercules system, with Pilot, KVH Gyrotrak/Halcyon Gyro, Vertical MHU, 2020s, Analogues, Remote Vision, etc, a Furuno 1722 radar/plotter at the nav station, a DY iAIS, a PC running Expedition talking to the B&G using the proprietary B&G HLink protocol and iPads running iSailor & RConsole to the PC. The radar gets AD10 heading from the B&G gyro, Expedition can provide alternating and context switched output channels to the B&G displays - for example pre start you can have time to gun, post start alternating mark bearing and distance, upwind target angle, downwind target boat speed etc. The iAIS will become a Vesper XB8000 or its SOTDMA successor this spring. It all works well, and does not require the PC to be working to do all the basics. This includes the MoB function: at present the MX412 looks after it all, with a remote push button by the wheel. 

Long story, but due to space restrictions in the nav station, and a longer term agenda to replace the radar once the doppler products settle down (B&G doing full ARPA like Furuno, for example), I'm going to replace the GPS with a B&G ZS100, and a Vulcan 5 as a display head, together with an H5000 Fastnet interface to pass the H2000 data to the N2K bus. I'll use the Vesper's GPS as a secondary source, as the 10Hz update of the ZS100 appeals. The Vesper will also bridge the 0183 and n2k networks, feeding GPS data back to the H2000. None of the current B&G plotters has an input for an MoB button. I might get MoB events on the N2K from the AIS beacons in our lifejackets, but they're not worn all the time and I want to retain a button on deck.

So, in my moving to an N2K world, how do I generate MoB events? I can (and will) plumb the deck button into Expedition, but I'd rather not be dependent on having a PC working, and running the right software, to track an MoB. It is usually, but inevitably won't be at the point when I need it most.

Re-reading this it sounds as though I'm a B&G loyalist - I like the sailing features, but the boat had the H2000 when I bought it so I've a significant existing investment, but the GPS & Vulcan are cost effective. The future replacement Radar could be from anyone, and I'd mirror the display to iPads on deck, but the current Furuno products don't happen to fit the bulkhead spaces I've got available terribly well. 

Thanks for the help,



Topic Tags
Ben Ellison
Member Admin
Joined: 1 year ago
Posts: 96
February 19, 2019 6:14 pm  

Hi Tom, I think that your request is quite interesting, and should be possible, but I'm a bit stumped about how. Googling around I found this Yacht Devices post...

...which seems to confirm that there are standard NMEA 0183 and 2000 MoB messages (relatively new, I think). But are they specific to AIS MoB devices, or more general? That may not matter, but then how do you get a standalone switch to issue a N2K PGN. But then again, YD has a new N2K circuit control and maybe they're willing and able to make MoB alert activation an option:

I also think that Vesper Marine would consider this a valuable feature and might consider adding another switch circuit to future models. Their MoB switch could trigger both the standalone alarm already included for AIS Mob, collision and anchor dragging plus maybe the N2K network MoB PGN.

I will alert both companies to this conversation but I may misunderstand some aspect.

Tom Henderson
Active Member
Joined: 3 months ago
Posts: 3
February 19, 2019 7:02 pm  


You're right on the money. I've found nothing, but had wondered about the yacht devices switch product, but I'm guessing it would need to grab a position fix from the bus to assemble the MoB message. A button input into the AIS is probably the best bet, as it is the kit I'm most confident will be on, and already has the position data. There is an Offshore Special Regulations requirement for a MOB button at the helm, with audible alarm below decks, but only in Cat 0 - essentially trans-ocean racing. B&G's H5000 processor has provision for one directly connected to the processor, as does A&T's - I'm guessing that NKE, Sailmon etc also do.

I'm sort of glad I've not missed an obvious fix. In the short term I'll rely on Expedition, it's, in my experience, by far the best sailing nav system (and Nick's support is extraordinary), but he advises against relying on it for good reason: it's not always running.

Feedback on thoughts from Vesper and YD would be welcome - it could be another reason to hold off waiting for the XB8000's successor!



Bill Kneller
New Member
Joined: 2 months ago
Posts: 1
March 23, 2019 10:18 am  


I recently installed a B&G H5000 Hercules processor with B&G Triton 2 and H5000 Graphic displays with a Zeus 3.  My previous instruments were Nexus that had push buttons by the helm to lock a heading number on the display (good for looking at wind shifts).  I repurposed the push buttons for MOB use.  The B&G H5000 Processor has an external MOB port that detects a switch closure. When the MOB button is pressed, the B&G displays on the N2K network can be set to show a man overboard graphic display with position, DR and rudimentary geo plot.  The Zeus 3 because of its display capabilities shows a much better geo plot.

I'm not sure if you are headed to a full B&G upgrade from your H2000 but if you do, this is native to the H5000 cpu with the Triton 2 and H5000 Graphics displays.




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