AIS & DSC MoB devices, the standards revealed

Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now pleased to have Ben Stein as a very able publisher, webmaster, and editing colleague. Please don't regard him as an "expert"; he's getting quite old and thinks that "fadiddling fumble-putz" is a more accurate description.

20 Responses

  1. Dan Corcoran (b393capt) says:

    1) Any chance the range would be substantially longer than 2 miles if the receiver is a USCG antenna integrated into Rescue 21 (e.g. very tall antenna)?
    2) AIS vs DSC? I guess I view this differently if I lost crew overboard and I want to get them back quickly (either option is fine), I am overboard and my crew is awake (which is more intuitive ?) vs. the only crew on board is asleep. In such a scenario, which is better DSC or AIS ? Which is more likely to get the attention of nearby boaters or the USCG?
    3) If I am the crew overboard, and my spouse is asleep, I would be very concerned she would be out of range before she responded. Would my chartplotter still have a symbol indicating where I was when I was in range or fell overboard?
    4) Do you see this technology being combined with Raymarine LifeTag like functionality? (Each LifeTag pendant broadcasts a unique identification code back to the LifeTag base station, telling it that its wearer is “safe.” In the event of man overboard, the link between the victim’s pendant and the LifeTag base station is broken and the alarm is raised automatically onboard the boat.)
    5) Maybe another interesting combination would be a Raymarine LifeTag like base station, in response to a LifeTag moving out of range, the AIS or DSC MoB beacon originates from the boat getting better range not to mention the Lifetags are much more wearable and less expensive in quantity.
    6) With any of these products, it would be neat if the device itself alarms if the wearer gets to far from the boat. Not so much for a crew over board function, but instead to warn the crew to return the device to me before they get to their car and drive home 🙂

  2. Sean Campbell says:

    While this unit does not have AIS it does have longer range VHF communications and GPS. It has an emergency feature that sends out GPS location to any VHF set within range. Available in dive shops:

  3. bwp says:

    While a great idea the general boating population has not only a lack of understanding of DSC/AIS functionalities but most of them don’t even have their DSC VHF’s connected to MFD’s. Those that do only 1 – 10 trust the technology and know how to use. On the AIS side in my area coastal NC my best guess is 1 in 30 boaters have AIS receivers. AIS more so than DSC scares the heck out of the average boater because they view it as a Big Brother tool …. goverenment intrusion into their personal lives.
    When I venture offshore I may see two AIS contacts a day, merchantmen transiting north/south. My Garmin 740 and Simrad NSS8 both display Sart AIS. When detected they place a symbol at the location of the emergency. That symbology remains in the systems until I delete it. So if you go overboard and everyone is sleeping the symbol will be there as a reference location.
    My statics come from personal experience. I do a lot of fishing club presentations in regards to safety and the integration with technology.

  4. SheltieJim says:

    I find this extremely exciting. Without knowing more details, it’s my inclination to wait for a unit that provides both AIS and DSC functionality — and I find it difficult to believe that providing both together would be significantly more complex (or expensive) than providing just one. And I’d be delighted pay a bit more for both.
    Dan mentioned the LifeTag system from Raymarine. I’ve got one installed on my boat and, although I’ve never needed its services for real, I can promise you that anybody on my boat who is not awakened by the alarm is already dead! That’s the kind of alarm that must be provided for use with these new devices, too.

  5. Thanks for the link Ben,
    A dual AIS/DSC MoB beacon is being developed by the Australian company Mobilarm
    The idea behind the new standard (I wrote the DSC section) is that a dual mode beacon will alert Merchant Ships/SAR aircraft, etc via AIS, and also alert all vessels in range via DSC. And, of course, only DSC provides an alarm on the bridge (as standard).
    Re Dan’s question re range. We conducted trials off Clearwater FL about a year ago in conjunction with the USCG. With a 1 watt DSC beacon floating at sea level, we were receiving it from out test vessel (33 foot fishing boat) at about 5nm, from memory.
    The local Rescue 21 CG station detected it at around 15 miles, again from memory.
    Happy to answer any questions.
    Glenn Dunstan

  6. Marc Dacey says:

    Ben, I discussed the “realities of self-rescue”, meaning the boat from which you fell off being able to be the boat that pulls you out, in my most recent blog post here:
    I think the AIS SART stuff is most promising, but only when linked to a proximity circuit to the AIS itself. If you have a 50 foot radius set on the device, or the properly equipped AIS “base station”, you don’t get far from the boat before all hell breaks loose.
    That covers the case where one is boomed, has had some sort of seizure or any other situation in which you are off the boat, your PFD has auto-inflated, but you cannot work the device.
    DSC is fine, but AIS gives you a better bearing directly to your sorry self in the water.
    So like you, I will await developments. Distance cruisers and ocean racers will find this most intriguing, but in coastal work, a PLB is still the better choice. Beyond the range of SAR folk, you have to be able to find the COB by coming about and unpacking the Life Sling or other device.

  7. John Konrad says:

    I’m reluctant to believe that DSC is the answer as I’ve seen too many false alarms broadcast over the system in recent years. I like the AIS SARTS a lot. I also tested the easyrescue last year and liked it, I also got my hands on the Kannad version for the first time this week and I’m impressed. But I think the solution is hybrid AIS/SART EPIRBS not DSC AIS SARTS. In the future I think AIS should replace the 121.5 homing signal still present in 406 epirbs.
    But what I like most is a simple waterproof radio so I can talk to nearby ships from the water. The perfect system for me would be a bluetooth handheld VHF with integrated AIS (not DSC) that I can clip to my lifevest. Here are the features I’d have in my ideal unit:
    -I’d like the unit to serve as a microphone to a base VHF (I have the RS-82 system on my boat) when in bluetooth range. When out of bluetooth range (like if I fell overboard) an alarm sounds on the base unit.
    -Water Activated, I’d like the following to go off when the unit is immersed
    –Strobe light
    –AIS tracking
    -Integrated GPS EPIRB
    -Two batteries
    –One for the emergency functions & one for the rest
    I know I’m reaching for the moon here but I think your best chance of survival in poor conditions (especially if you are the captain of your own boat) is being able to actually talk with the surrounding boats.
    Surrounding boats (especially commercial ones) are likely to ignore a DSC alert but will NOT ignore someone asking for help on Channel 16.

  8. Hello John
    I find your comment that surrounding boats will ignore a DSC alert rather puzzling. A DSC alert from a MoB beacon will contain position information and a valid MMSI.
    AIS is a very good technology for MoB, but it suffers from 2 disadvantages:
    1. It is not fitted to a wide cross section of ships (yet, anyway); and
    2. It does not ring an alarm (as standard).
    AIS will eventually become very widely used by all classes of vessel, but in the interim, the best solution for MoB alerting is a combination of AIS/DSC.

  9. John - gCaptain says:

    1) While many boats under 1600 tons aren’t required to carry AIS, all ships certainly are:
    2) If your vessel is carrying AIS/SARTS then, whether through your own AIS system or a dedicated MOB alarm system, you are certainly going to make sure the units alarm the bridge which can then alert other vessels nearby.
    Do DSC devices provide active tracking of MOB’s? I think this is a critical feature.
    “A DSC alert from a MoB beacon will contain position information and a valid MMSI.” Yes but it has been well documented that DSC suffers from a very high false alarm rate and thus is ignored by most mariners. I agree that a combined AIS/DSC system may have some value (although I’d like to see an AIS/PLB or AIS/VHF combo unit first) but add unfamiliarity to commercial mariners propensity to ignore undesignated or automated DSC distress calls and I think your chance of a ship diverting to help you – if DSC is your only means of signaling your distress – is slim.
    And it has been my experience that most boaters are even less familiar with – and their systems less capable of handling – DSC calls than commercial mariners.
    I’ll even step out on a limb and suggest DSC has been largely ignored by mariners (and boaters!) and thus is essentially useless. The program should be scrapped and rebuilt from scratch.

  10. Ben Ellison Ben Ellison says:

    “Yes but it has been well documented that DSC suffers from a very high false alarm rate and thus is ignored by most mariners.”
    Where’s that documentation, John? I do know about the famous case in New York Harbor — and wrote about it here: — but I’ve never thought of false DSC alarms as pervasive.
    I agree that DSC is “largely ignored by mariners (and boaters!)” but I still hold out hope that it will become more widely used as the tools get better.

  11. John - gCaptain says:

    Where to begin? A google search of the topic brings up 162,000 results ( ) including academic papers written about this topic ( ) and a list of special circulars from the IMO. It’s also the #2 topic for discussion at the upcoming NATIONAL GMDSS IMPLEMENTATION TASK FORCE in May and has been a hot topic of the committee for many many years.
    What’s most troubling are statements like this on the IMO’s GMDSS FAQ page: “At the same time, the GMDSS system makes it possible for the ship in distress to be contacted, to check whether the alert is real or false, before search and rescue operations begin.” Statements similarly worded litter the USCG and other SAR organization websites making you wonder if even the professionals are numb to the problem.
    But I agree with you that, although we may disagree on specific points about the future, Glenn’s website is a treasure of quality information on the topic. Including these two which discuss the problems with false alarms:

  12. John - gCaptain says:

    As far as your statement ” I agree that DSC is “largely ignored by mariners (and boaters!)” but I still hold out hope that it will become more widely used as the tools get better.” I hold out hope too.
    Upon reflection I also need to clarify my wish to scrap DSC. I believe the underlaying architecture is excellent and holds promis but the way DSC is viewed by the commercial, rec and SAR end users needs to be scrapped and I believe the manufacturers need to start over. While I’ve seen some great improvements in recent years, the user interface on most ship gmdss radio units (I won’t even touch more archane features like NBDP) makes those MKD displays you dislike feel like an iPhone… which is part of tge reason AIS is being danatically adopted by end users with little to no training. Like sn iPhone AIS just works and, once you’ve used it you wonder how you lived without it.
    Personally I love DSC and use it frequently for, not only nav warnings and distress, but also collision avoidance ( and routine calls. But I’m a mariner tech-geek and thus in the minority.
    The best analogy I have heard is with text messaging. Cell phones have had this feature for decades but it never caught on in tge states untill the iPhone showed us how really cool it is. Sure texting had some core users, as does dsc (myself included), and you read lots about how Eutopeans and othrrs lived texting but Snericans couldn’t be bothered because it was difficult to type on small phones and no one saw tge point when calling someone is “just as easy”! The same goes for DSC!
    Lastly the uscg, SAR community and publications (panbo and gcaptain are both guilty to some extent) are the buggest obstacle to it’s implementation gor hhe simple fact that most talk about dsc is in the context of safety. Untill it’s use as a basic, and effective, ship-to-ship communication tool is known it’s not going to peak the intrrest of gge average sailor.
    (Those are just my thoughts but I’m open to debate!!)

  13. Ben Ellison Ben Ellison says:

    The Kannad and McMurdo personal AIS SARTs both got FCC approval on Friday, which includes lots of interesting documentation and test info for techies. Go to the FCC search site:
    Use (parent) company name Orolia for “Applicant Name” and “AIS” for Equipment Class…

  14. Tiberio Marri says:

    My 2 cents…
    OneMan AIS SART W420 here :
    and a AIS SART Sniffer (to improve a quick alarm when a AIS SART is activated) here :

  15. Steven says:

    Hi everyone,
    The discussion on PLB’s is more vivid as ever and I’ve been reading this thread with great interest. But I did notice some interesting things, especially being in a commercial boating enviroment
    1: a lot of you see AIS systems as more safe than DSC devices, this is weird since it is a lot more common to ignore AIS-alatms than DSC alarms (especially with the integration of ECDIS systems imminent).
    DSC however falls under GMDSS regulations and will always trigger a reaction of those using it, false alarms are usually in designated DSC-alarms with no position. Also it’s mandatory to log an alarm received via DSC. Something thats abcent at AiS
    2: I’m looking around for a PLB but I’m reluctant to get a 406Mhz one because of the time it takes to get a response (middle of the ocean or high lats.) In the worst case it can take up to 90min for the RCC to get a fix on you, then starting up the operation and all… AIS and DSC alarm ships close enough to respond…however when they’re slightly out of range its useless.
    I keep looking and perhaps talk to some superiors about getting a system in our PFD’s.

  16. Stan L-B says:

    Seems to me there is a device missing from the MOB manufactures equipment that I have browsed. In a high sea situation, as in your image – it is extremely difficult to keep sight of any object floating. From my personal experience it would be beneficial if a MOB had a self inflating hydrogen balloon system with at least a three metre line attached to the flotation device. On my ocean going yacht I have made up a simple mouth inflating rubber balloon which is attached to the flotation device – it works!
    Stan. L-B
    RNSA -Gosport

  17. Jorgen says:

    I clicked into the web page of They seem to prioritize posting big photos of the management and not a single link to where one could learn about their product line. In ten years time expect them to be a case study in business schools…

  18. Jorgen says:

    This is an old thread, but nonetheless I give it a shot.
    If you are a solo-sailor the discussion takes on a new dimension as there are no one on board to take action. And yet – there is! Today our boats are full of gear that most be put into the first line of defense the sailer builds up.
    I have the “standard issue” of a PLB and a AIS-sender attached to my life west. In addition to this I have a NASA MOB system, which does the same thing as the Rayarine (which by the way is now no longer on the market): When the sailor is more than some 10m away from the unit, an alarm goes off. In addition to this, the autopilot is engaged and the rudder is put to full starboard. The motor is turned off. And finally the rear anchor starts dropping (no matter if it get contact with the bottom after 40m, it will act as a brake on the boat and perhaps even provide a helping hand to reestablish physical contact with the boat).
    Several other actions can be taken. This season I will add the function of dropping a floating rope from the rear of the boat. I probably also will drop the front anchor. Its rode is longer, and I have become a little anxious about what will happen if the boat should turn in a way that would lead it directly over my position in the water! So better have the boat braked down and risk the rodes getting mixed up.
    I will also work on a solution to the problem which have played out in harbors where I have jumped off the boat in order to attach the first line – and then heard the machinery behind be jump into action in order to save me.

  19. Ben Ellison Ben Ellison says:

    Sounds like quite a solo MOB system you’ve worked out, Jorgen. I’m not sure there’s anything more you could do.
    Incidentally, the Mobilarm site is not really active. Mobilarm, sMRT and Sea Marshall apparently all merged and trade as Marine Rescue Technologies:

  20. Marisela Lora says:

    Nice article – I was fascinated by the facts . Does someone know where my assistant might be able to obtain a template FCC Form 740 example to fill in ?

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