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Cake day: June 18th, 2023

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  • 802.11ax, clients just… (essentially) wait for a random amount of time, listen for a break in the signal, and take a leap of faith.

    Ethernet originally worked the same way, back when it competed directly against token ring. Ethernet won by being as reliable in real world scenarios while being cheaper to build out. Gigabit Ethernet was the first standard that insisted on full duplex only.

    Half duplex mode with the collision avoidance is still actively supported for 10/100, but it is becoming very hard to find an unswitched hub. So you may have to write up your own twisted pair cables.


  • When you enter the United States, customs “inspects” all the stuff you’re bringing back. If it’s more than $850 worth of stuff, then you have to go to the cashier and pay a tax.

    The tax is a percent of what the stuff is worth. The percent rate can depend on what type of goods it is, and what country it’s coming from. There are massive tables to look this stuff up.

    The stuff you carried out of the country and are now bringing back with you doesn’t count toward the $850 limit.

    If you’re shipping stuff in but not traveling with it, there is no exemption. Tax applies right away. You also have to hire a guy called a broker to help you with the CBP paperwork and to submit payment.

    So let’s say somebody is importing sugar from the Caribbean, and there’s a tariff. They have to pay a percent to the feds every time they ship in some sugar. They raise the price they charge on the sugar to cover that. Then sugar from Louisiana looks more attractive on the store shelf because it’s cheaper.

    Who pays? Whoever is shipping the goods in pays, but they make it up by charging more for the imported products.

    Why do it? Usually, you want to make some domestic industry more attractive by raising the price of the foreign competition.

    In the sugar example, sugar is more expensive to farm in Louisiana because people get paid more, and the equipment is more expensive. If there wasn’t a tariff, people might stop farming sugar in Louisiana entirely. That might make some people sad. On the other hand, all Americans would be able to pay less for sugar without the tariff.





  • (not a lawyer). If you bought the game copies that the AIs are playing, then it seems like you’re not making a copy of the game just to have the AI play it.

    That kind of assumes that your AI is playing the game through a mechanism like AutoHotKey, generating keyboard or controller inputs that pass through the operating system to the game.

    If your AI hooks into or modifies the game code to “play”, then it could run afoul of anti-reverse engineering clauses that are common in the click through license agreements. Those clauses may not be enforceable in your jurisdiction. Legal results on anti-reverse engineering clauses are kind of mixed in the United States.

    Edit: for reference, there was a software called “Glider” that played World of Warcraft for you, so you don’t have to grind to level up. Blizzard absolutely hated the makers of Glider, but it stuck around for a long time, before it was ultimately sued into oblivion.


  • Here’s my guess. I don’t know anything about this particular device, but I have worked with medical devices.

    A powered exo-skeleton sounds like it might be a class II medical device. Being a medical device, the OEM was required to produce a safety risk analysis per ISO 14971 in the EU and 21 CFR 820 in the US. I don’t know what all was listed, but probably one of the safety risks was thermal runaway from the (assumed) lithium ion batteries.

    Lithium ion battery packs have a well known problem with occasionally overheating and catching fire. This famously delayed the launch of the 787 Dreamliner. This is also why you can’t put your phone or laptop battery into your checked luggage.

    In the original risk analysis, there will be a number of mitigation steps identified for each hazard. For the lithium thermal runway, these probably include a mix of temperature monitoring, overheat shutdown, and passive design features in the battery pack itself to try to keep the impacts of over temperature and fire away from the patient.

    So how does the price get to 100k? It could be some kind of unique design features that are now out of production and the original tooling is not available. The 100k cost is probably something like to redesign the production tooling, particularly if you have to remake injection molds.

    You can’t just use any off the shelf battery pack, because that would invalidate the risk analysis. You’d need to redo the risk analysis, repeat at least some amount of validation testing, and possibly resubmit an application to the FDA.

    TLDR: you can get some MEs and EEs together to solve this problem, but once they’re on the case, you can blow through 100k real fast.




  • Medical devices are required to comply with 21 CFR 820 in the United States, which establishes quality management standards. This includes minimum standards for the software development lifecycle, including software verification and validation testing.

    In the EU, broadly equivalent standards include ISO 13485 and IEC 62304.

    If an OEM wants to do a software update, they at minimum need to perform and document a change impact analysis, verification testing, and regression testing. Bigger changes can involve a new FDA submission process.

    If you go around hacking new software features into your medical device, you are almost certainly not doing all of that stuff. That doesn’t mean that your software changes are low quality–maybe, maybe not. But it would be completely unfair to hold your device to the standard that the FDA holds them to–that medical devices in the United States are safe and effective treatments for diseases.

    This may be okay if you want to hack your own CPAP (usually a class II device) and never sell it to someone else. But I think we all need to acknowledge that there are some serious risks here.


  • The line items look like a pretty standard “workup”, as they call it. The blood and urine tests are probably a fishing expedition to make sure you don’t have some other bizarre disease. If it turns out you did have this hypothetical bizarre disease, I’m sure you’d be disappointed if the emergency department missed it.

    $7k CT seems pretty steep, but CTs are also a marvel of modern technology. I know MRIs have a price floor because they need medical grade liquid helium for cooling, which is thousands per liter. I don’t know if CT has a similar consumable item or not.

    I would hazard a guess that most real kidney stones would be revealed by x ray. But it’s also possible that x ray would not reveal other physiological abnormalities that could be causing your symptoms.



  • Another aspect to this is that Android is Linux, but it is not GNU / Linux. This is true both in the literal sense of not using GNU coreutils or glibc, and also in the broader sense.

    What I mean by the “broader” sense:

    • no X or Wayland
    • GTK or Qt support is something an application has to bring with them.
    • filesystem is substantially reorganized
    • users and system permissions setup substantially differently

    To the application programmer Android / Linux looks like a completely different ball game.


  • I thought they catch fire and burn down slowly.

    Correct. Both the recent pager and radio attacks, and the 1996 cell phone attack, were performed by planting military explosives inside the devices in advance.

    There is no magical way to hack the electronics to make a lithium battery straight up explode.