A problem with our security beacons in case of MOB

[Gilletarom]

Hello,

Recently, one of our MOB security beacons was triggered by chance. The MMSI number of this beacon had been entered (we believe) in Options/Boat/MMSI OpenCPN.

No reaction from OpenCPN and yet the AIS was in operation!

Explanation, the MMSI entered was incorrect, but this number began with 972. It looked like a number from a message sent by a personal MOB beacon.

All MOB personal beacons have an MMSI that starts with 972 for us, and it seems to me that this is universal. SO, an idea came to me.

Why, if an MMSI number starting with 972 is received on the boat, by the AIS, since we are "certain" that, in this case, there is a man overboard in the environment of the boat, would not an alarm be triggered automatically displayed by OpenCPN?

And this alarm should not require any adjustment of OpenCPN options.

[Wotname]

Yes, 972 yy zzzz is reserved Man overboard DSC and/or AIS devices. Also note 970 yy zzzz for Search and Rescue Transponders.

More info on MMSI leading digits - https://en.wikipedia.org/wiki/Mariti...rvice_Identity

[requiem]

Can you briefly describe the specific circumstances? E.g. "was about to do a test inflation of the PFD and forgot to disarm it; plastic cover flipped off and it started blinking...." How quickly did you realize it was triggered and what happened then? For example, the MOB1 has a 15 second delay before it actually starts transmitting.

As for the entry in OpenCPN, it should be easy enough to pop open the preferences and verify both the number and the preferences (tracking / no-tracking, treat as MOB, etc).

Ah, one last question: was the beacon detected via AIS and it was just the lack of an explicit MOB alert that was the issue, or did it not appear at all?

[Gilletarom]

Originally Posted by requiem

Can you briefly describe the specific circumstances? E.g. ......

Hello Requiem,

Hmm... It seems to me that you are a little off topic.

Regardless of the initial reason for my reflection, only my final request matters, namely, that an alarm is triggered automatically, in OpenCPN, if the AIS receives an MMSI number that begins with 972.

The only limitation could be that the MOB is not too far from the boat.

Gilletarom.

[svmobert]

Have you looked at this?

https://opencpn.org/wiki/dokuwiki/do...ttons:ais:sart

[Corsair63]

let's say that cannot understand the question.

regardless of registered in the options menu or not it should trigger the alarm, because as you said it a MMSI registered as SAR beacon.

we should have to ask first, why the alarm was not triggered?

it would be a good start for a program bug, I guess.

[Hakan]

Originally Posted by Gilletarom

Regardless of the initial reason for my reflection, only my final request matters, namely, that an alarm is triggered automatically, in OpenCPN, if the AIS receives an MMSI number that begins with 972.

The only limitation could be that the MOB is not too far from the boat.

Gilletarom.

A SART, i.e. with a mmsi starting at 97, does trigger an alarm, and a MOB if stated in mmsi-properties, if, and only if, it's reported status is "Active". Otherwise it's handled as a test message and a SART target is drawn and the AIS target table is updated. But neither alarm nor mmsi-properties MOB.

else if (Class == AIS_SART) {
    if (NavStatus == RESERVED_14)
      navStatStr = _("Active");
    else if (NavStatus == UNDEFINED)
      navStatStr = _("Testing")

Are you sure your device has really sent an "Active" message and not a "Test"?

[Gilletarom]

Originally Posted by Hakan

A SART, i.e. with a mmsi starting at 97, does trigger an alarm, and a MOB if stated in mmsi-properties, if, and only if, it's reported status is "Active". Otherwise it's handled as a test message and a SART target is drawn and the AIS target table is updated. But neither alarm nor mmsi-properties MOB.

else if (Class == AIS_SART) {
    if (NavStatus == RESERVED_14)
      navStatStr = _("Active");
    else if (NavStatus == UNDEFINED)
       navStatStr = _("Testing")

Are you sure your device has really sent an "Active" message and not a "Test"?

Hello Hakan,

Yesterday I returned to the boat to test the beacon.

- On the opencpn screen, I never saw a display telling me that the tag was being tested.

- On the other hand, I was able to observe the triggering of the beacon signaling a man overboard: red flash, sound signal (after having chosen it).


But :
- I do not understand what the purpose of the declaration in the "Options/Boats/MMSI" page of the MMSI of the beacon is,
- nor what is the point of saying, in this same page, that this MMSI must be considered as that of a MOB tag.

I will need to retest this beacon more carefully to better understand.

[stevead]

I do not understand what the purpose of the declaration in the "Options/Boats/MMSI" page of the MMSI of the beacon is,
- nor what is the point of saying, in this same page, that this MMSI must be considered as that of a MOB tag.

I understand this option is to allow you to specify a "normal" MMSI number (one that does not have a 970, 972 or 974 prefix) that when a transmission is received is displayed as an alert. Used for some of the MOB fobs.

IIRC quite some time ago, Hakan and myself verified SART/MOB/EPIRB and DSC Distress alerts and all were displayed correctly. SART/MOB/EPIRB devices under test (which have the AIS Navigation Status set to 15, instead of 14) do not generate an alert, but are still displayed correctly.

However it seems that Options/Ships/MMSI preferences and setting a MMSI number to be displayed as an alert does not work as expected. Could someone else verify if this is indeed yet another bug?