Testing AIS MOB beacons, ACR’s DSC feature especially

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.

29 Responses

  1. Walter says:

    Curious, if you name the MMSI of a AIS MOB in you MFD, say “Walter’s MOB” what would the MFD show during an alert or test.

  2. Ben Ellison Ben Ellison says:

    Hi Walter, I doubt that the AIS MOB alert would change, but maybe the MOB icon would get the “buddy” if your MFD has that feature. I’ll give it a try (and also meant to see how PC Charting programs like Coastal Explorer and TimeZero handle an MOB test.
    Incicdently, there are dedicated AIS MOB alarms that let you name the beacons on your boat, both from Ocean Signal and Digital Yacht, I think.

  3. Richard C says:

    Let me say up front I really like the AIS MOB device concept. In fact, I purchased the ACR AISLink last spring to put in my new Spinlock PFD. This started me down the road to some minor disappointments. First, The AISLink didn’t fit in the Spinlock so I felt I had wasted money when the intention was to have this deploy automatically while stored inside my new PFD. But just for the hell of it I tried installing it in the old Mustang Hydro-static PFD, the one I keep onboard for crew, and it fit just fine. ACR AISLink is just a hair too big for the Spinlock. This left me without an AIS MOB so I purchased the Ocean Signal and it fit inside the Spinlock perfectly.
    Like Ben did, I laid out all the little pieces that came with the device and read the instructions. My first impression, “This is a first generation, almost primitive way to do what I know will change down the road”. Why can’t the AIS MOB manufacturers pick up the phone and call the PFD guys and talk about a standardized way to quickly and securely install an AIS MOB in any PFD? Come on ACR, Spinlock, Mustang!
    When you look at the picture in Ben’s post it’s a collection of cheap string, plastic doodads with tape and ribbon. I was hoping for something more positive then leaving the integration of the AIS MOB product with PFD up to me to figure out. After the install I can say “I think” I might have it right, but only a MOB situation will prove if it will deploy as it should. Not that the device is the issue here. If it fails to deploy it will be all my fault for not getting the plastic pieces snapped together properly or the black ribbon wound around the bladder in the right direction or the string – I think the string is still on my desk.
    So, if you see what I mean, cooperation between PFD and AIS MOB manufacturers could make this installation a fool proof, drop it in the pocket and clip to the bladder and you’re done, type of simple, foolproof confidence building experience.
    I won’t even get into the “flashing light on the computer screen” programing routine. Didn’t they ever consider using a micro USB port? Well I’m not a computer tech so maybe there is a good reason why easier programing methods were not used here.
    I’m happy I bought the two devices, no regrets, I think they will work, but I just see lots of room for improvement when it comes to having the end user fold it into a PFD.

  4. Ben Ellison Ben Ellison says:

    Thanks, Richard, great points except I disagree about the optical programming. It might be unfamiliar, but it was just as easy as a wired connection, I thought, and a lot more waterproof.
    I notice that Spinlock sells a deck vest already fitted with an MOB1 and also has video about how to do the install:

  5. Richard C says:

    I see your point on the optical programing being waterproof, certainly a USB would not be waterproof no matter how hard they tried. This is the first time I ever came across the “optical computer screen flash” method of programing anything, but it did work for me the first try.
    Yes, the MOB1 fit perfectly and this is the one I purchased after realizing the AISLink was too big for the slender design of the Spinlock Deckvest.
    I did try to find a vendor that sold the Deckvest with the MOB1 pre-installed, but it seemed no one wanted to take a chance and stock this option. The local vendor I spoke to told me that his problem was aging stock. As soon as he receives his supply of Spinlock PFD’s they begin to lose value as the inflator has a replacement date. He went on to say that the Deckvest with MOB1 has few customers interested in this costly added option and therefore they may sit on his shelf a very long time depreciating in value.
    So…, no inventory in the store means customers can’t buy the Deckvest with installed MOB1 and Spinlock thinks no one wants one. In my opinion, this is a good reason for Spinlock to sell direct.
    Standardizing the way an AIS MOB is installed in any inflatable PFD would take the possibility of user installed error out of the equation and insure proper activation should the PFD be deployed for the real thing. Standardization would take cooperation between PFD and AIS MOB manufacturers, something only the brave would attempt.

  6. chriggel says:

    I can confirm that the Standard Horizon Matrix GX2200 fixed VHF works just nicely together with the Kannad R10. The alarm is loud enough and the display tells you exactly the bearing and distance to the casualty. Also the AIS SART test mode is well suported.

  7. Ben Ellison Ben Ellison says:

    Thanks, Chriggel, and kudos to Standard Horizon. Now I notice that they advertise AIS SART display right near the top of the feature list:
    Moreover the manual indicates that the GX2200 supports AIS MOB beacons and EPIRBs too, and the response sounds good, as you noted. I will correct my entry.
    I also note that the GX2200 can receive (and send) DSC Distress Relay messages, so maximum AIS MOB beacon support from Standard Horizon. I imagine these features extend to other SH VHFs and VHF/AISrx models, but I’d check the specific manual to be sure.

  8. Xavier Itzmann says:

    I haven’t yet tested our Smartfind S20 nor our Kannad R10, but just now sailing 6 miles away towards Athens, someone fired 3 tests from 970117847 (4:15pm, 4:18pm, 4:39pm, 4:46pm), with the following results:
    B&G Zeus (3.0.12): Dialog on screen, 3 messages on the AIS list page. No audio alarm.
    B&G Zeus2 (older software 4.5, before the current one with the Audio/Autopilot sidebars): Dialog on screen, 3 messages on the AIS list page. No audio alarm.
    B&G V50 VHF with AIS ON: SART AIS Target? What’s SART? Yeah, I got all the AIS targets in the area, but the MOB? Never heard of him. He can drown for all I care!
    I wonder if the lack of audio alarm is by design or if I have some obscure setting off.

  9. Ben Ellison Ben Ellison says:

    Thanks, Xavier. The MMSI starting “970” means that actually was an AIS SART (Search and Rescue Transmitter) being tested. AIS MOB devices start “972” and EPIRB-AIS beacons start “974”:
    SARTs are essentially bigger, commercial versions of personal AIS beacons, meant to locate lifeboats better than the radar transponder type SARTs.
    And all of them, including the new AIS EPIRBS, use AIS in the same low power local way and come preprogrammed with MMSI numbers.

  10. Tobias says:

    I am not sure the DSC regulation is correctly stated. I think one problem is how ot is broadcasted. Namely, do the devices only send the alert – or do they also have a receiver, which detects the acknowledgement (implying: repeated broadcast until ack, then silent)? I think the only AIS MOB which has a receiver is Weatherdocks’ easyRESCUE-PRO, which is bulky and expensive. At least last time when I checked, all others only broadcasted w/o being able to receive the ack, hence, the repetition is limited and also to whom it is transmitted – and this also relates to which DSC call is permitted in a given country.

  11. daniele banfi says:

    Correct, The last ITU DSC standard report very clear that in DSC MOB operation, the MOB unit shall be receive and manage the Ack message…. in fact if the MOB have no receiver inside, is out of ITU requirement.

  12. daniele banfi says:

    more clarify in MOB operation in DSC , see ITU M.493-14 paragraph 16

  13. Ben Ellison Ben Ellison says:

    Hi Daniele,
    I do not have access to ITU M.493, so if you have a link to it, that would be great.
    Are you saying that devices like the ACR AISLink with limited DSC transmission (by regional authorities) and no DSC receiver are illegal? I’d be really surprised.

  14. Wince says:

    As far as I am aware this is free to access and the recommendation can be downloaded in several languages.
    This recommendation has been implemented by ETSI standard EN 301 132, which requires the MOB to have a receiver so that acknowledgements are received and acted upon (tests in section 10). All ETSI standards are freely available. This one is at http://www.etsi.org/deliver/etsi_en/303100_303199/303132/01.01.01_60/en_303132v010101p.pdf

  15. Ben Ellison Ben Ellison says:

    Thank you, Wince! The ETSI document is particularly interesting, though I remain confused. A DSC receiver seems clearly called for, but then again there is no test procedure given Closed Loop (your own boat or MMSI group only) DSC distress alerts.
    I also note that the labeling recommendations reference two distinct types…
    Open loop devices shall be marked DSC-MOB-O.
    Closed loop devices shall be marked DSC-MOB-C.
    …though the types aren’t referenced again.
    Finally, I found the EU Certification for the ACR AISLink, which is dated October 2017:
    It does note that “DSC functionality may vary to comply with National Regulations; the device has only TX-functionality” but that’s what I tried to explain above.

  16. Simon - SRT CEO says:

    SRT has been developing radio communication devices for a wide range of applications for over 25 years. We have been looking at MOB/PLB’s for a little while, and how AIS could be used, but as yet not brought a product to market. This is due to our concern about real world performance due to the physics of radio propagation. Although we have developed an AIS SART.
    The new em-trak B400 high powered Class B, and A200 Class A all have a special MOB alert, track and find application. This instantly generates an alert if an MOB/PLB (SART) transmission is received and brings up a radar type display showing the bearing and distance of the most recent received transmission. As a matter of note, the IEC standards for Class A state that a SART transmission must generate an alert and go to the top of the master vessel list.
    However we feel that the main issue is one of the physics of radio and how that works when a radio device is attached to a person who is immersed in water – in particularly in regards to AIS.
    Leaving aside the issues related to size of device and antennas, the main issue that we have seen is that if such a device is used in rough weather it is likely to be quite unreliable due to waves blocking GPS reception and or AIS transmission. For optimal and reliable performance the GPS and VHF antennas need to be clear of the water and as high as possible. This is of course quite easy to achieve, but then compromises the everyday convenience of the product.
    The electronics of an AIS MOB/PLB are very simple since it’s just a simple AIS transmitter, who’s performance and operation are defined by the relevant specifications. However the challenge for us manufacturers is the physical implementation of the product such that it is low cost and easy to wear whilst on the boat, but also when needed, that it also works reliably and safely and the user’s real world performance and functionality – even in rough seas and bad weather.
    Its an area we will continue to look at, but remain concerned that the natural laws of physics might win on this one!

  17. Anonymous says:

    Reference the DSC debate, this morning I quickly asked our Customer Support team about this and their reply was as follows:
    “Reading the DSC standard it’s clear that DSC receivers are optional, and in the AIS standard it is specifically not required. The additional power required to run a receiver will require a larger battery etc., unless you can assume the distress signal will be acknowledged and the MOB can elect to stop transmitting sooner rather than later, then maybe the same size battery could be used. I can see that if you’re in the water receiving an acknowledgement would be a great comfort, but it doesn’t help you to be rescued in anyway. One may prefer to use the available power to transmit for longer.”
    I hope this is of help.

  18. Wince says:

    I’m not sure which DSC standard is being referred to as EN 303 132 states in section 5.1:
    “Transmission shall only commence if the channel is not busy (Listen Before Talk). The locating
    beacon shall have an integral DSC receiver capable of receiving distress acknowledgements.”
    So there are two reasons it is necessary to have a DSC receiver – make sure the channel is clear and receive acknowledgements.
    I agree there is no such requirement on AIS MOB (as defined in EN 303 098). But I am confused by the statement “it’s clear that DSC receivers are optional” as to me the standard (EN 303 132 as listed on the AISLink type approval certificate) is very clear that they are a requirement. I would love to know what I am missing!

  19. Simon - SRT CEO says:

    Earlier today I posted a quote in relation to the DSC requirements. Our Test & Compliance Manager has pointed out that what I posted was INCORRECT. My apologies for any confusion caused – this is entirely my fault in cutting and pasting in haste from an internal email within our Customer Support Department. I should have checked with the right people in SRT who deal with these matters daily.
    The correct position as far as we are concerned is as follows:
    According to the global DSC standard ITU-R M.493-14 for both an ‘open loop’ and ‘closed loop’ MOB device using VHF DSC, both a receiver and transceiver is required. The MOB is required to cease transmitting the distress alert when an acknowledgement is received and indicated to the user as described in section 16.6. This is backed up by ETSI EN 303 132 (which is a European Standard) which requires that a receiver and transmitter are required, and made very clear in Figure 1 of the ETSI standard (see below). The fact that ACR has had the AISLink device ‘type approved’ under the relatively new ‘Radio Equipment Directive’ (RED) may be technically OK as the RED requires devices to meet the relevant ‘essential requirements’ of the directive, which isn’t necessarily every last word of any given standard. These essential requirements are listed on the RED certificate and are generic requirements focused very much on the health and safety of the user, electromagnetic compatibility, and the effect on radio spectrum usage. Of the twelve essential requirements listed on the certificate only four are deemed relevant to the AISLink by the notified body, none of which specifically require compliance with any particular standard. However, The type approval certificate states that AISLink is compliant with EN 303 132 v1.1.1 which it is not, if it doesn’t have a receiver. Therefore one assumes that it does have a receiver if this is what is being claimed and has been tested and certified.
    Again, my sincere apologies for my error.

  20. Ben Ellison Ben Ellison says:

    Simon, the RED certificate notes that the ACR aisLink does not have a DSC receiver (as I quoted above):
    “DSC functionality may vary to comply with National Regulations; the device has only TX-functionality”
    And if RED is about essential requirements, that makes sense to me. I don’t see how unacknowledged 0.5 Watt DSC closed loop calls could cause much trouble, and I believe that the open loop calls allowed in some jurisdictions are a single automatic burst — no acknowledgement required — and single manual bursts after that, again no acknowledgement required to end transmission.
    I’m no expert on this (or much else ;-), but I do think the DSC MoB routines were designed to avoid a receiver so as to reduce device size and cost.

  21. Wince says:

    I’ve done some digging as this does not make sense; how can a DSC MOB be certified when it does not meet a requirement of the defining standard?
    The only place I have been able to find that gives the possibility of not having a DSC receiver is in the RTCM 11901.1 document (as referenced in 47 CFR 95.1403), which states:
    “If the AU uses DSC messages addressed to ‘all ships’ as the alerting mechanism, the AU shall be fitted with a GNSS receiver to provide location in the transmitted message and a DSC receiver solely for the purpose of receiving acknowledgments of distress calls.”
    Where AU = alerting unit.
    Which suggests that if messages are not addressed to ‘all ships’ then a receiver is not required. It also means the only reason that a DSC receiver is required is to receive acknowledgments.
    From the AISLink MOB manual it is clear that the only ‘all ship’ message supported (when enabled due to geographic regulations) is a manually triggered single transmission, which Ben rightly points out, does not need an acknowledgment.
    As the RED (Radio Equipment Directive) needs compliance with its essential requirements of health & safety, EMC, spectrum usage and special requirements, it is possible that ACR have argued that it meets these without meeting all the requirements of the European standard (EN 303 132).
    This is a very interesting example of how the international standards and the various certification processes do not lead to a clear understanding of the functionality and performance of products in the marketplace. Something I personally feel is not particularly satisfactory.

  22. John - gCaptain says:

    Hi Ben, Any word on units that combine both AIS and PLB functionality into one unit? I know FT-Tech was working on the SEAANGEL SA16+ which combined these features but I haven’t heard a release date yet.

  23. Ben Ellison Ben Ellison says:

    Hi John,
    I too am enthusiastic about a PLB/AIS combo, and was glad to meet the FT-Tec crew in Miami last February, but I haven’t heard a word about this becoming a real, available product:
    I really hope that the SeaAngel hasn’t fallen into the regulatory hole where the Standard Horizon GX6500 combo VHF/AIS Class B seems to be stuck, but was heartened to hear a rumor that Ocean Signal is also working on a PLB/AIS.

  24. John - gCaptain says:

    Agreed, thanks Ben!

  25. Daniele Banfi says:

    The MOB DSC require a DSC receiver to accept ACK and check that the DSC channel is free.

    This is part of last ITU rule and EN303132. Also you can check at Annex A of EN303132 that somes test regarding receiver are Unconditionally Applicable (i.e like 11,12 and 13)

    I.e. in Italy, a primary international distributor that sell a AIS+DSC MOB have received a alert from Italian Telecomunication Department to avoid to sell product that don’t have DSC receiver inside (and in fact stop to sell the product).

  26. Hi Ben! We had purchased a pair of S10 beacons two years ago, but in a fit of stupidity, I succeeded in losing one. After looking at units at the Annapolis Sail Show (and being unable to buy one there as they sold out on Thursday!) I ordered an ACR/ARTEX AISLink on Amazon.
    It arrived, but the box came only with a tiny pamphlet (in 7 languages!) that told you how to activate the unit (I think – the print is VERY small!) – but with no explanation of the various bits of plastic, string and stickers included. The box did have a URL for Artex so I went there, but finding the actual instruction manual for the unit was not easy (there is no reference to it until you go look at the “Product” page for the unit itself – the “Support” tab has nothing).
    Its a bit intimidating, but I’ll get thru it and install the unit in Lesley’s PFD later this week 🙂
    Didja get my email re: Fatty Knees?

  27. Ben Ellison Ben Ellison says:

    Hi Hartley, ACR doesn’t make it easy but this links to AIS Link manual is very readable PDF form:


    Have you tried to program your VHF MMSI in yet? For that you’ll need the Windows or browser app:


    And sorry I failed to follow up on what sounded like nifty Fatty Knees mods. I’ll dig for it

    • HI Ben – Thanks! I did download the programming software, but was unable to get the unit into “program mode” – the lights were NOT doing what the software called for, and it failed to communicate. Now that I have instructions, I may be able to figure out what is going on. But the sun is out today, so I’m working on Atsa’s bilge sump project (requires a dry bilge).

  28. Craig Warner says:

    We recently tested an Ocean Signal MOB1 Rescueme DSC/AIS. We tested the DSC function. When we pressed the test button, our hand held VHF radio got the DSC distress message but not our main VHF (Standard Horizon GX2150). We doubled checked for the correct MMSI and the numbers matched. We called Standard Horizon, and they informed us that radios over four years old were not programmed to receive DSC messages from personal man overboard devices. Our radio needed a firmware update. Standard Horizon provided the upgrade for free with free return shipping. I thought readers with older VHFs and planning to purchase AIS man overboard personal devices would want to know of this. Be sure to test your device and make sure the correct MMSI numbers are programmed into your VHF radios and your man overboard devices.

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