How electric space heaters start fires

While planning and reviewing our electrical work, I found that on YouTube, many electricians chronicle their experiences, and I've learned a lot from it, especially about what problems are common and how they manifest themselves. (Yes, I'm a Senior Member of the Institute of Electrical and Electronics Engineers, but I know more about what goes on in a MOSFET than in a breaker panel. I have a great respect for electricians and for the research that is embodied in the codes that they follow. When I was four years old, I wanted to be an electrician, but I got sidetracked.)

Big point: Electric space heaters often start fires, but not the way you think.

The heater itself has lots of safety features built in to keep it from catching fire. To learn all about them, watch this video. Some of them surprised me, such as a thermo-mechanical positive feedback loop... I'll let you watch and learn, without spoiling the suspense.

No; space heaters set wires and cords on fire, not the heater itself.

To make that clearer: space heaters stress-test your wiring by taking the maximum amount of power allowed, and unlike other high-power appliances, they aren't used in kitchens wired for heavy current (like toasters), nor used just for a short time (like circular saws or hair dryers). Space heaters are left running unattended for hours in places with ordinary 15-amp wiring.

When high current is drawn through a connection that is not quite perfect — maybe corroded, maybe loose — the connection heats up. It heats up in proportion to the square of the number of amps, so when you pull 10 amps through, you get 100 times as much heat as with 1 amp. Your desk lamp and laptop might work just fine on a slightly dubious outlet that can't safely sustain a space heater.

A typical space heater draws 1500 watts (12.5 amps), and the most a typical outlet circuit can safely supply is 15 amps. What's more, the circuit includes several outlets and maybe some lights.

Hint #1: Never use 2 heaters on full power on the same circuit (which usually means in the same room).

Hint #2: Never power a space heater through an extension cord, outlet multiplier, adapter, or power strip. Always plug it directly into the receptacle. If you have to have an extension cord, a heavy-duty air-conditioner-type extension cord rated at 20 amps is probably safe, but you are still introducing more connections that can overheat.

Hint #3: Keep an eye on the plug and receptacle. After using the heater for a few minutes, make sure its plug, and the outlet it plugs into, are no more than slightly warm. That's where overheating is most likely to take place.

Click here to see a video of a particularly gruesome case (gruesome to the equipment; the people weren't hurt), where a space heater was plugged into an outlet multiplier (and I think there may have been other things wrong). My link takes you right to what you need to see; the rest of the video is somewhat rambling.

Hint #4: Don't use full power if you don't have to! Most electric heaters have a half-power or low-power setting. If you cut the heater wattage in half, you are cutting the amps in half, and there will be only a quarter as much overheating from a bad connection (due to the square law).

Hint #5: Watch out for symptoms of defective wiring:

• If lights dim more than slightly when the heater comes on, your wiring is inadequate or you have a poor connection, which is going to overheat, somewhere in the wiring in your walls.
• One LED bulb can easily flicker by itself (LED bulbs do that), but if two or more lights flicker in unison, you have a poor connection or overload that is deteriorating, and probably heating up, while you watch. That could also be the case if only one light is flickering, if there are no others on the same circuit for you to compare to.
• If lights (maybe in another room) brighten when you turn on your heater (or any other appliance), you have a more serious problem called an open neutral or high-resistance neutral, and you need an electrician. This problem affects how the incoming 240 volts are split into two 120-volt phases, and if uncorrected, it can fry some of your equipment by giving it too much voltage.

One last note. Almost all the electrical appliances in our homes have gotten tremendously more energy-efficient over the years. Lights draw 1/7 as much power. A TV set draws 50 watts rather than 500. Even air conditioning is more efficient. Despite inflation, the power bills for my house are smaller than what my mother paid, in the same house, 45 years ago, even though the house has been added on to!

The main things that haven't gotten more energy-efficient are those that use heating elements: stoves, ovens, irons, and electric heaters. The reason? They are already converting all the electricity into heat, and it's not possible to do better than 100%!

There is one way to get more heat with the same amount of electricity. That is to use a heat pump and move heat from one place to another. That's how my home office is heated. Air conditioners are heat pumps working in the opposite direction; you can't convert electrical energy into coolness, which is lack of energy; so what you do is move heat out of your house into the outside air. In the winter, a heat pump moves heat from the outside air (which is chilly, but not infinitely chilly) into the interior of the house. (You can extract heat from air even if it's already colder than the thing you are wanting to heat; air conditioners and heat pumps use compression of the refrigerant to pack more heat into a given volume of matter.) A heat pump is energy-efficient but not good at spanning large temperature ranges.

I thank Brian Burtt and Clay Turner for contributing useful information in the Facebook conversation that this entry grew out of.

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Major electrical upgrades to our house

Further to the flickering-lights problem that I wrote about last month, on January 18 our house underwent a major electrical upgrade. But first, let me show you what was wrong.

This is the circuit breaker that was removed last month. Look at the contacts where it clips to the bus bar. You're supposed to be seeing shiny metal, not corrosion.

This picture, taken after the old panel was dismantled, shows what it was clipped to. Look at the corrosion — and notice that the tab below it was just as bad. So were quite a few others. This was serious trouble about to happen.

So we got a new breaker panel and a new service — that means we replaced everything that brings power into the house except for the meter itself, which belongs to Georgia Power Company. Here is the service entrance, where power comes in from the underground power line:

Unlike the old meter housing, the new one has a small box below it containing the main circuit breakers for the house, plus a whole-house surge protector. That means power for the whole house can be cut off from outside. That is a boon to firefighters, who might want to cut power in an emergency without having to go inside and hunt for the breaker panel! It also means that all the cabling in the house is circuit-breaker-protected. Previously, if the main entrance cable had shorted inside the house, there would have been no way to power it off without calling Georgia Power.

Here is the new breaker panel. Installing it in a closet was not a good idea (on the part of the builder in 1974), and we decided to take down some shelves that were to either side of it. That led to a lot of sheetrock repair, then painting, finally finished today.

And here's the inside:

I made the big orange numbers with a Brother labelmaker; the small numbers embossed in the panel were too small to read. I also added some printed documentation about various features of the house's electrical system, and especially, two charts of which breaker goes to what:

I know I'm unusually thorough, but I'm accustomed to computer systems that can't possibly work if hundreds of details aren't right. Notice that I also kept track of the old circuit numbers (from the previous panel), since they are written on some wires and outlet covers.

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How to label your circuit breakers

About those charts shown above, here's my advice about how to label your circuit breakers.

• Do it. It takes time, but you can either spend the time to do it all at once, or waste a lot of time every time you need to find a circuit breaker. Besides, if you're ever going to sell your house, good labeling adds value. It marks the house as well taken care of.
• Do it in a spreadsheet so you can sort it both by number and by location. That's how I did it.
• Describe rooms by location, not by occupant, so the names will be permanent. One of my original breakers was labeled "Tim's room" and Tim's family moved out in 1977. Our new nomenclature says things like "front corner bedroom" and "back middle bedroom."
• Be prepared to make corrections as you discover minor mistakes or make changes to the wiring.

For help finding breakers without turning off the power, I recommend a Sperry CS550A circuit breaker finder. With adapters, you can also connect it to light sockets. Although Sperry doesn't say so, its transmission can also be picked up on an AM radio, so you can use a small transistor radio to trace the positions of cables in walls.

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AI slop, visual

This picture is a microcosm of what's wrong with the way people are using generative AI. It was posted on LinkedIn by Linn Titcombe, who received it as an ad for a local restaurant.

Her comment: "When businesses put things like this out, it sends all the wrong messages. OK, it may be free [artwork], but at what cost? Unprofessional, incorrect information, and a lack of attention to detail. I mean, these people are eating outside in the snow!"

Indeed! AI-generated pictures usually have garbled writing. This is no exception. The large-scale and small-scale details are right, but the mid-scale is wrong — thus you get neat lettering but nonsense spelling, and an overall reasonable-looking scene with blunders such as — eating outside in the snow.

To me, this signals something worse than carelessness.

All too often, AI-generated text and art, especially art, indicates disregard for truth. People just want something that looks nice or sounds nice. Correspondence to reality doesn't matter, so they don't check or edit what they've generated.

If these people don't care whether their advertising picture makes sense, do they care whether their food is stored and cooked safely?

I've seen AI-generated pictures in local-history groups, and if they're not labeled as such, they are lies. (If they are labeled as AI, they are probably useless, but at least the harm is mitigated.) I recently saw something that was probably a striking example: supposedly a picture of Valdosta's Brookwood Plaza shopping center in the 1960s. The thing is, I lived in Valdosta in the 1960s (as a child), and I don't remember the Woolworth's sign being big and red with white lettering. That's what an Australian Woolworth's sign looks like. I think that's what someone's AI pasted in. And it's not historical truth!

Too many people's AI ethics seems to be, "Let me see how many people I can fool!"

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Canals of Mars — real but a thing of the past?

As most of you know, many telescopic observers of Mars, especially Percival Lowell (active 1893-1908), saw or thought they saw narrow streaks on Mars, named "canali" or "canals." The Mariner space probes startled everyone by proving that there were no such things. Apparently, observers, expecting to see streaks, would interpret irregular mottle as a blurred image of streaks. The human eye and brain work that way.

Now consider this. The way dust blows around on Mars, maybe there were a few prominent streaks around 1900 that had disappeared by the space-probe era. Even one unmistakable streak could set people's expectations.

The only way to test the plausibility of this hypothesis is to wait for some future Martian dust storm to create a prominent streak.

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Available for public speaking

I am available to give talks to audiences on all levels, from high school up, about AI and related issues. Click here to see more.

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A coming upsurge of superstition?

This and next two items are things I recently posted on LinkedIn.

Hypothesis: The technology shock, from society getting used to generative AI, may lead to a period of proneness to superstition, just as the technology shock of the 1950s and 1960s led to the upsurge in the 1970s of horoscopes, "mysticism" made up on the spot, pseudoscience such as biorhythms, and the like.

There's a difference. In the 1970s, people didn't think their TV sets were gods. Now, though, it will be easy for people to think of generative AI systems as supernatural beings (good or evil), since generative AI can imitate anything, real or mythical, that it has ever seen a description of.

On the brighter side, it may also lead to something else we had in the 1970s — a desire for a broad humanistic education. People may realize that they don't want to be totally dependent on machines, that they want the knowledge and the tools of thought that previous generations had.

Keep your eyes open.

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AI-assisted writing

It's not whether you use AI to assist with your writing, it's whether you have something to say in the first place and whether you take responsibility for the content and style of what you end up publishing.

The problem with "AI slop" is that people who have nothing to say are using AI to generate text that says nothing or is inaccurate, and not taking responsibility for it.

(Including style. I think, under the surface, one thing that annoys us about AI-assisted writing is that we often see an unsuitable, Dr.-Seuss-like style.)

I don't write with AI, but I probably would if I needed to deliver an extended text in German or French. I've been a writer in English for decades and a machine probably can't help me much. In other languages, though, I would welcome help and would particularly rely on the machine's ability to get the grammar and spelling right.

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AI-assisted computer programming

Is "vibe coding" (AI code generation) just the next step up from compilers and assemblers?

Not exactly, because compilers and assemblers are deterministic, and AI code generation (by LLM) is not deterministic -- it is a probabilistic sample.

I have no doubt AI code generation is useful, used with due care. But it makes me ask another question: Is it telling us that our programming languages are too low-level, and that we need to be programming with higher-level units (API components, etc.) that more directly reflect the specifications in the first place?

(For example, does anybody remember how miserable Windows programming was for the first few years, before we had a high-enough-level API for the windowing and mouse actions?)

Code that is easily written by AI may be code that shouldn't need to be written at all.

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What's scaring people about AI

The thing that is scaring people about AI — the hot issue in AI ethics right now — is not the humanlike behavior of the software.

It is that people are putting unreliable software in charge of things that can harm human beings.

Until now, we've used computers because of their extreme reliabilty (within limits). That's why you'd rather have your bank account calculations done by a computer than by clerks with pencils.

Machine learning produces approximate outputs, and generative AI produces, at best, educated guesses. Everybody is going to have to start thinking about imperfect reliabilty and how to measure it.

And get used to using generative AI for rough estimates and suggestions, not final answers!

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Turtle

Today I wanted to get my two Nikon CoolScan slide scanners working. (They have to be used occasionally to keep the lubrication on their mechanisms from getting too sticky.) To try them out, I opened a slide album and picked a slide — a picture of our pet turtle in the mid-1990s. Enjoy!

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Current on the ground wire

While reviewing our planned electrical work, I came across something else that is seldom explained well, and even electricians (or at least handymen) sometimes misunderstand it. It's why the neutral wire is tied to ground in only one place.

Here is how electricity normally enters a house. I've left out the circuit breakers, and I've shown half of the transformer unconnected; normally, half of the 120-volt circuits use one side of the transformer, half use the other, and the 240-volt circuits use both.

The live and neutral wires deliver power. The ground wire is only protective; its purpose is to make sure that the metal cases of appliances, metal outlet boxes, metal pipes carrying wires, etc., can't shock you.

The ground wire goes to a metal rod driven into the ground. It is tied to the neutral wire at only one place, normally the "first point of disconnect" where your main switch or main circuit breaker is. (In our older house, it's in the breaker panel, but it will be moved to be outdoors, near the meter.)

Ground and neutral are tied together to ensure that the neutral wire is never at a very high voltage, and that live and neutral cannot, together, be elevated to some dangerously high voltage through an accidental connection to something else.

Here is how current normally flows. Every electron that comes out the live wire goes back to the transformer through the neutral wire (or the opposite, on the opposite half-cycles of the alternating current).

Live and neutral deliver the power that does the work; ground is a protective connection to the case or housing of whatever you're powering. Small, low-power devices such as radios often don't use a ground connection; they have a two-prong plug that may or may not distinguish live from neutral. More about that here.

So what happens if neutral and ground get tied together again downstream? Knowing they are tied together at the entrance, some people mistakenly tie them together again somewhere else, in an outlet box or inside an appliance. Then this is what happens:

Now the ground and neutral wires share current, and oops! The ground wire is carrying a heavy current, which it wasn't designed to. If this happened downstream from a GFCI, the GFCI would trip, but if it were in an outlet box, that probably wouldn't happen.

Here is a particularly good demonstration that makes it clear what happens. In that demonstration, the voltage difference from neutral to ground was probably only about 5 volts, not enough to shock anybody, but the available current was 22 amps, about a third of which ended up flowing through the ground wire. (And probably heating up the alligator-clip lead that the man was using to demonstrate the accidental connection!)

About putting the main breaker outdoors, with the meter: This newer practice makes it possible for firefighters, or anyone discovering a fire, to cut electricity to the whole house from outside it. That can be lifesaving. The way our house is built right now, if it caught fire, we'd evacuate the bedrooms first, and then be unable to get to the main breaker, which is in a bathroom closet!

It also ensures that there is no wiring in the house not protected by a circuit breaker. Right now, if there were a short in the main cable from the transformer, that could easily be inside the house, upstream from the main breaker, and we wouldn't have any protection from it.

Why do I write things like this, when nobody is paying me? Well, why does a violinist play the violin when not preparing for a concert? I write partly to stay in practice, and partly because I enjoy finding good ways to explain things. Expository writing is in my blood.

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Calculus puns

(Out of mercy I will not name the people who helped me continue this series of plays on words; the first one is my own; it all happened on Facebook.)

Among many other controversial claims, Karl Marx argued that calculus is ill-founded because derivatives involve dividing by zero.

Hearing this, I remarked, "See? Marxism knows no limits."

One replied: "The Eagles sang, 'Take it to the limit one more time.'"

I said: "That's a second derivative pun."

Another replied: "The puns are accelerating."

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Circuit breakers, AFCIs, GFCIs

We are about to get some major electrical work done on our house, including the addition of a large number of AFCIs. (I have been adding GFCIs piecemeal for years.) In looking at people's conversations and videos, I see a lot of things being misunderstood, so, in order to have something to point people to, I'm going to try to make a few things clear.

Basic electricity: Complete beginners may not realize that electricity does not flow out of an outlet the way water flows out of a faucet. Every electron that comes out one of the slots in the outlet (live or neutral) goes back into the other slot. Along the way, it passes through something such as a light bulb, where it gives up some energy and gets some work done, such as lighting the light.

Think of electricity as like a saw — doing work by being dragged across or through something — rather than like a fuel that is fed into something and consumed there.

In fact, a saw is a particularly good example because we use alternating current — it switches direction 120 times a second (taking 1/60 second to go through the full cycle; that is what we mean by 60 Hz). (50 Hz in Europe.) Saws work that way too, switching direction as they go back and forth, and doing work on both strokes if suitably designed (which is more important for electricity than for handsaws).

Protective devices: Now to what I was going to write about...

Circuit breakers are located in the breaker panel (fusebox). They protect against:

• Overloading, too much current being drawn through a circuit, such as when you plug several space heaters or vacuum cleaners into outlets that are fed by the same wires.
• Short circuits where the live and neutral wires are touching, either inside an outlet box, inside a cable, or inside an appliance; or when the live wire is touching the ground wire. Circuit breakers trip only if the short circuit is a good, consistent unwanted connection and lasts at least half a second or so.
• Both of these things are fire hazards.

Note: "Short circuit" does not mean "loose connection." It means electricity is flowing freely from the live wire to the neutral or ground wire without doing any work (except heating up those wires and eventually starting a fire). Of course, a short circuit can be caused by a wire coming loose and solidly touching another wire.

AFCIs (arc-fault circuit interrupters) are a relatively new invention and are usually combined with the circuit breakers. They protect against:

• Loose short circuits where wires are touching lightly, causing intermittent sparks (arcs).
• Loose connections, breaks in a wire or connection where contact is still being made some of the time, causing sparks as contact is made and then lets go.
• Both of these are also fire hazards.

AFCIs detect sparks by the way they start, stop, and resume very suddenly, causing current to start and stop on a microsecond timescale. That is true whether the sparking is caused by a loose short circuit or just a break in a wire that is carrying current. Some old types of electric motors normally have sparking inside and can trip an AFCI.

GFCIs (ground-fault circuit interrupters) are usually built into outlets, and can protect additional outlets that are wired through them, but they can also be built into circuit breakers. They protect against:

• Mismatch between current flowing out and coming back, indicating that some electricity is escaping into something outside of the wiring, or possibly into the ground wire.
• That is often a situation where a human being would receive an electric shock, such as by touching a live wire while standing on the ground, or dropping an electric hair dryer in the bath water.
• Because the house electric system is grounded, escaping electricity makes its way to the ground (the earth) through soil, water, water pipes, or the grounded outer frame of an electric appliance. That's why this situation is called a ground fault.
• GFCIs protect against electric shocks, not fires.

Some people think the GFCI detects current flowing into the ground wire. It does not; in fact it does not even need a ground wire. The GFCI detects a current imbalance between live and neutral.

Most importantly, none of these protects against all electric shocks, nor against all possible electrical fires. Circuit breakers protect against the worst short circuits. AFCIs protect against many more short circuits, since short circuits almost always arise gradually and start out loose, and also protect against loose connections that are not shorts. GFCIs reduce the risk of electric shock in situations where water or damp ground are involved.

But if you touch both the live wire and the neutral wire, you will get a possibly fatal shock; the wires won't know you're not an electrical appliance.

Likewise, you can still use power from the wires to overheat something and start a fire, though with AFCIs, you could only do it with something that consumes current as steadily as legitimate heaters, lights, and the like; a loose or worn-out wire is not likely to do it.

I have come to feel that AFCIs are the more important of the two, but both AFCIs and GFCIs are needed. Why shouldn't we be as safe as we can be?

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An hour in the 20th Century

Yesterday (December 31) I spent an hour in the 20th Century, or so it seemed. I went to the post office to mail a letter and actually went up to the counter to make sure there was enough postage on it. Then I went to Kroger, and after picking up a prescription, bought a newspaper.

Two things that were unlike the 20th Century were the extremely smooth-running engine of my car (much smoother than anything not microprocessor-controlled) and the fact that at no point did I smell cigarette smoke, which used to be the unavoidable smell of public places in America.

The newspaper was, in fact, the very final print edition of the Atlanta Journal-Constitution (AJC), the newspaper all Georgians grew up with. Melody missed an opportunity to work for this newspaper when I plucked her out of Atlanta to get married and move to Los Angeles in 1982. She was then working for the newspaper in Marietta.

When we were children, the Journal and the Constitution were separate newspapers, combined only on Sundays. The morning paper, the Constitution, was printed in the dead of night and trucked all over Georgia so that it was, in fact, our morning paper even in Valdosta, and we got the local Valdosta Daily Times in the afternoon.

The AJC continues, of course, as a web site for subscribers.

It has been more than 20 years since we had newspapers delivered to our house. The Internet has supplanted them, but imperfectly. The problem is pricing. Much Internet news is free, totally ad-supported. Major newspapers, however, still require subscriptions, which few people feel the need to pay for (we don't). We're aware that we get appreciably less local news than we used to. This effect may in fact be tearing apart the fabric of towns, turning small cities into mere suburbs with less of a local identity.

I wish they could make themselves fully ad-supported. The key to it may have to do with how you see the ads. In a print newspaper, the ads are something you look through — almost like a city directory — particularly the classifieds. On the Internet, as on TV, ads are things that intrude into what you are doing. Is there a way to turn them into something interested shoppers will actually browse through, the way they did newspaper ads?

I don't know how much the AJC was selling for normally, but the price of the final issue did strike me as a bit daunting. Eight dollars can pay for a lot of Internet access.

It was a poignant moment when I sat down to read the day's Atlanta newspaper for the last time. I had not done so in years, but it's something I did almost every day for decades.

I didn't read everything of course; just as in the old days, I looked at maybe a quarter of what was there. But there were entertainment items that I would always look at because they were there, even though I didn't seek them out on the Internet: the comics (in color in this issue), the Jumble (a word puzzle), and Dear Abby, whose first question this time was about a chatbot.

Other printed newspapers still exist, but this old familiar one is gone.

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Who is this "Penny Rounding"?

In keeping with the spirit of the 20th Century, I paid for the newspaper in cash, and to my surprise there was a new line item on the receipt, "penny rounding." Kroger gave me a 4-cent credit in order not to have to give me pennies, which are being discontinued by the Mint.

It appears that Kroger always rounds in the customer's favor. The other way to do it is to always round to the nearest multiple of 5 (thus 1 and 2 round to 0, but 3 and 4 round to 5; my price of $8.64 would have rounded to $8.65).

I've already seen people on Facebook saying, "This rounding always makes you pay more, it's another sneaky trick." No, it doesn't. Someone shouldn't have slept through elementary-school arithmetic. Rounding to the nearest multiple of 5 should be fair, assuming the price before rounding can be anything. Of course, if a merchant were to arrange for the prices after tax to always end in 3 or 4, they'd gain a few cents, but it would take a lot of effort.

There's a simple way to eliminate the problem. Round the amount of sales tax to the nearest 5 cents.

No, I didn't say change the tax rate, which is what people usually think I mean when I say that. The tax can remain 8%, as it is now. The tax on $10 will remain 80 cents. But the tax on $1 would not be 8 cents; it would round up to 10. Likewise, the tax on $1.50 would not be 12 cents; it would round down to 10.

If the amount of sales tax were always a multiple of 5 cents, and the merchant's prices were always a multiple of 5 cents, no further rounding would be needed. The merchant would not be taking a loss or a gain — just collecting the amount of tax prescribed by law. Numbers that are not multiples of 5 cents would disappear from our economy.

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