Content nonwithstanding, announcing rule changes like this with immediately taking effect is just shoddy practice. At least give travellers a few weeks of heads-up.
So how do most European airlines have just that on their intercontinental flights?
I don't think I've flown intercontinental without universal power sockets (accepts EU & US plugs, sometimes others, voltage info hard to find) in the past 10 years.
In some cases it's sadly still a premium cabin thing. I refuse to fly economy at this point, premium eco tends to be good enough to get power sockets.
> In the US, not disclosing a password is explicitly protected (5th amndmnt),
That's great but of exactly zero help if you're trying to travel to the US and CBP (or ICE) are staring you down. Even if they don't gulag you, they can always just reject entry for any non-citizen (and these days even some citizens it seems.)
Any country can reject non-citizen entry, for any reason or no reason at all. In fact, part of a definition of a country is ability to practice control over its territory and who is and is not there. This necessarily includes border controls, which any country can decide to make as onerous as they please. No non-citizen of a country has any right to be present in it, except as permitted by its government, so any country if free to make it as hard as they wish to enter for non-citizens. This may not be a good idea, but control over a territory is literally part of the definition.
> Any country can reject non-citizen entry, for any reason or no reason at all. […] This necessarily includes border controls, which any country can decide to make as onerous as they please.
Or, a country could set rules that specify what they will and won't do as part of their entry controls. Just because it's a kind of an "absolute" power doesn't mean you can't still self-impose rules. The benefit being attracting more leisure and business travellers.
Yeah, it used to be that you could still make calls (particularly to emergency services) even in complete power outages, for as long as your local exchange has batteries for. (AFAIR that tended to be on the order of hours, but probably differs quite a bit across locations and regulatory domains/countries.)
Another thing we lost in the age of VoIP landlines, but then again mobile towers also have batteries. Just don't be unlucky and have a power outage with 3% battery on your phone...
> I then learned that the energy draw of running the low-volt transformer all the time - especially one large enough to supply an entire house of lighting - would more than cancel out energy savings from powering lower voltage fixtures.
That's not a constraint of physics, you can absolutely build a DC power supply that is efficient in a wide load range. (Worst case it might involve paralleling and switching between multiple PSUs that target different load ranges.) But of course something like that is more expensive...
> But of course something like that is more expensive...
More expensive than an inefficient unit, but it should still be a lot cheaper than 120 separate units, right?
And I expect one big fat unit to do a better job of smoothing out voltage and avoiding flicker than a bunch of single-light units. Especially because the output capacitors are sized for the entire system, but you'll rarely have all the lights on at the same time.
Though for efficiency I'd think you'd want 48v and not 12v.
"We went a little over the line to figure out where the line is, so, we can now guarantee you, dear shareholder, that we're extracting the absolute maximum possible value! Isn't that splendid!"
> If you went 48 straight to POL voltages then you would have horrific converter performance.
What's horrific converter performance in numbers?
An isolated flyback (to 12V) should be able to hit >92% and doesn't care if it's fed -48V or +48V or ±24V. TI webench gives me 95% though I'd only believe that if I'd built and measured it. What's the performance of your -48V → +48V?
[with the caveat that these frequently require custom transformers... not an issue with large runs, but finding something that can be done with an existing part for smaller runs is... meh]
-48 to 48 claims something like 97% (load dependent of course). It also needs to arbitrate between two input supplies for glitchless redundancy, plus have PM bus and other spec mandated stuff. There is no technical reason why you cant go -48 -> 12 as you state with good efficiceny, but we cant get hold of a part that ticks all the boxes.
Horrific performance by my definition would be 48v to say 1v. We only realistically use buck topologies for POL supplies. Such a ratio is really bad for current transients, not to mention issues like minimum on times for the controller.
I'm just surprised that either input isolation isn't on your spec, or it still somehow works out better with isolated to +48V than straight to 12V... but I guess if your spec requires other things, it makes sense.
Well if it's negative 48V the electricty flows out of your circuit and back to the grid, so you need to make it positive to have the electricity come in.
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