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submitted 9 months ago by xkcdbot@lemmy.world to c/xkcd@lemmy.world

xkcd #3169: EPIRBs

Title text:

'Oh no, the box is drifting out into the harbor!' 'Yeah, I wouldn't worry about losing it.'

Transcript:

Transcript will show once it’s been added to explainxkcd.com

Source: https://xkcd.com/3169/

explainxkcd for #3169

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[-] neidu3@sh.itjust.works 124 points 9 months ago* (last edited 9 months ago)

For those who didn't know: EPIRB = Emergency Position Indicating Radio Beacon. Sends an emergency signal via satellite and terrestrial RF. They can be triggered manually, but they also trigger automatically if salt water shorts two exposed pads for a certain amount of time (a minute, I think).
Once triggered it will get a GPS fix and transmit a distress signal via satellite as well as terrestrial VHF. It is programmed with the MMSI of the ship it belongs to.
Works all over the world, although they take a bit longer to successfully transmit the signal in the polar regions as they then have to rely on LEO sattelots in polar orbits.

Source: I have a GOC, and I also used to work with marine electronics. I've programmed hundreds of these. Mainly ~~Jordan~~ Jotron TR60 (Ducking autocorrect). Some from McMurdo too, don't remember the model name.

Fun fact: A coworker did have to make the phonecall of shame to the coastal radio after accidentally dropping one overboard.

[-] mossy_@lemmy.world 19 points 9 months ago

what does programming them include? Just a ship identifier?

[-] saltesc@lemmy.world 20 points 9 months ago

I have a handheld one—to float with me in a liferaft, etc—and it gets registered to a vessel or vehicle. Whenever I want to use it on something different, contact the federal government, advise of the new vessel ID or vehicle registration, and it's now associated with the new one.

I don't think it matters much since it is a beacon after all, but I think it helps in searching. Also, a lot of other details are registered along with it so they know who to send the tens of thousands in fines to if I somehow bypass all three "Are you really sure?" switches and fire the thing off inappropriately.

[-] neidu3@sh.itjust.works 6 points 9 months ago* (last edited 9 months ago)

Any chance what you have is not an EPIRB, but a SART? SARTs are only registered with beacon ID and doesn't require programming. Shows up on radar and sometimes AIS also. No sat comms involved.

[-] saltesc@lemmy.world 4 points 9 months ago

Registration Status: Registered.
Beacon Type: EPIRB.
406MHz GPS (Cat. 2) 66-channel. Beacon Status: Operational.
Battery Expiry Date: 01/10/2028.

It's UIN—which I obv won't give lol— doesn't hold an MMSI. The main reason being EPIRBs aren't just for marine craft.

[-] neidu3@sh.itjust.works 12 points 9 months ago

It's been a while, but off the top of my head: MMSI (which is basically the radio installation identifier. Same number is used for AIS), and an ID digit (0 in wheelhouse, 1 on starboard bridge wing, 2 on port, etc)

[-] mossy_@lemmy.world 3 points 9 months ago

nice, so plug it into a laptop, get it programmed, then drill it onto the ship?

[-] neidu3@sh.itjust.works 10 points 9 months ago

Yes, except no plugging involved: It's some sort of inductive way of programming it via a USB dongle. The info is written into this "programming program" which can read and write data to the unit, it's written, and then you read it to make sure all the info was applied.

Then you label the unit physically with ship name, callsign, and MMSI. In addition to this there are two stickers that come with the unit, denoting the expiry date of the battery and the hydrostatic release. These go on the unit so that's it easy to check if it's time to replace them.

[-] SkaraBrae@lemmy.world 66 points 9 months ago

When I worked for a scrap metal recycler someone dumped a load of electronics and didn't tell us there were EPIRBs in the mix. We found out when the cost guard, police, fire and ambulance turned up.

[-] ripcord@lemmy.world 2 points 9 months ago

Wait wtf were they doing dumping them in the ocean

[-] BanMe@lemmy.world 1 points 9 months ago

Nautical crackheads will strip beacons right off the waves. In broad daylight.

[-] SkaraBrae@lemmy.world 1 points 9 months ago

Dumped at the scrapyard... In a three-sided, concrete-walled bay in the yard, 30km from the nearest large body of water. I didn't say anything about the ocean.

[-] ripcord@lemmy.world 1 points 9 months ago
[-] Kowowow@lemmy.ca 10 points 9 months ago

The coast gaurd get an @everyone

[-] bjoern_tantau@swg-empire.de 7 points 9 months ago

What are you zinking about?

this post was submitted on 17 Nov 2025
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