jcrawfordor

When the tower was constructed in 1887, multiplexing technology was probably not available (I'm not so sure of the timeline in Europe). By 1913 it likely would have come into use. However, multiplexing really isn't a factor here, as the tower seems to have been built to serve local loops. Since these loops go to subscriber telephone sets, there's no option for multiplexing without expensive and maintenance-intensive equipment at customer premises. Multiplexing of local loops is called "pair gain" and wouldn't be developed until later, and it was never really that popular in most phone systems. Outside of suburban areas, it's typical that each copper pair runs directly to the exchange. Historically, and today, there is rarely any active equipment (or since the 1950s or so even passive conditioning) on local loops, they're just wires from the exchange to the phone.

As for why you didn't see similar constructions in other cities, this was definitely an unusually large telephone office for the time. In the US, a city exchange of the late 20th century would usually have just hundreds of lines, many of them multi-party. Telephone companies scaled up by building more exchanges, rather than a single very large one. When they got into these kinds of subscriber numbers at an exchange, the F1/F2 cable scheme was in use to avoid this kind of wiring. It does seem to be the case that telephone adoption was unusually rapid in Sweden, I find one (poorly sourced) claim that there were some 4,800 telephone subscribers in Stockholm in 1886 which would very likely make it the most telephone-rich city in the world. The situation of the tower seems to have developed in part because its builder, Allmänna, was consolidating the Stockholm telephone market through acquisitions and made a decision to centralize the many acquired customers onto on exchange.

What I'm a little confused about here is the lack of cables. The other big reason you didn't see constructions like this in the US, even in places like New York City, is because subscriber loops were quickly moved into lead-sheathed, paper-insulated multi-pair cables. These could contain hundreds of pairs. Cables were pretty much reaching maturity when this tower was built. I am curious as to the reason that multi-pair cables were not adopted more quickly in Stockholm, but it may be as simple as the considerable investment in this tower making open wire the preferred option for its short lifespan. In any case, the common claim that underground cables obsoleted the tower rings hollow to me, or at least misses an important detail, as aboveground cables were already in use in the 1880s. I suspect that modernization to cables was just deferred in Stockholm until it happened to also make sense to move to duct or pipe systems. In the US, it was more common that telephone exchanges switched to overhead (aerial) cable to manage exactly the wire sprawl issue that this tower exemplifies, and then only later (if ever) started to bury cables.

This article has more photos of the tower, but unfortunately not much more technical history: https://rarehistoricalphotos.com/the-stockholm-telephone-tow...

And this includes some photos of other parts of the Stockholm telephone network. The tower was not the only impressive construction required to manage this many open-wire pairs: https://thehistoryinsider.com/when-the-sky-over-stockholm-wa...

I wouldn't take these Truth in Accounting reports too seriously. They're linked to ALEC and take a very hard-right stance on fiscal issues, and in particular, this report on NM (which is also nearly five years old) seems to ignore the permanent funds---as best I can tell they are lumping them all under "restricted" and ignoring them, even though the land grant permanent fund, the largest of them, is totally at the discretion of the legislature and the others are very broad. The permanent funds are also now significantly larger than that report shows.

While NM has debt it has been servicing it fine and state revenue has increased year over year pretty much since that report was produced in 2020 (either 2020 or 2021 were the worst years for the state's financial position). It's projected that 2025 will close out with nearly $3.5 billion in unspent revenue, and the state has about $50 billion saved in various permanent funds. The state's financial situation is currently so good that it has allowed things like universal free college tuition in a largely revenue-neutral way due to the significant balance of the invested funds.

One of the main criticisms you will hear of the NM legislative on the fiscal front is that they are too hesitant to spend money, since NM has serious issues with underperformance in areas like education while also having billions of savings that could be spent down in an effort to address those issues (and in fact the state supreme court more or less mandated the state to start doing so several years ago). However, since NM's revenue is so tied to the oil and gas industry and its boom-and-bust nature, the legislature likes to keep a substantial cash reserve to manage the bust years. That may be particularly important right now as the Trump administration is radically reducing the amount of federal funding that NM receives, which has always been a critical revenue source due to the state's high level of poverty (third highest in the US or so, depending on year and how you measure).

Yes! I will draw a slightly roundabout connection here to my pet topics, the British shared a number of fuze concepts as part of the Tizard mission and designs based in large part on the British concepts were developed and tested at the New Mexico Proving Grounds, part of what would later become Kirtland Air Force Base. Much of this work was directed by physicist E. J. Workman, president of the New Mexico School of Mines.

I could probably rewrite the above sentence to improve it, but I focused on the magnetron because it was seen to be of special significance at the time (directly addressed issues that US efforts at e.g. MIT Radiation Laboratory were struggling with) and that there's an interesting story surrounding the couriering of the "most secret" magnetron to the US (it was briefly lost). These were the early days of "classified" as a concept and consistent techniques around safeguarding classified matter hadn't been developed, so the magnetron plays an interesting role there as well (along with documents on a number of topics, but I believe the magnetron was the only "physical artifact" brought by the Tizard mission).

I'm referring to the Tizard mission exactly, in which Cockcroft brought a magnetron to the US for show and tell. Nuclear weapons were less of an emphasis than radar (and jet engines, also a UK-led development) at that point in time.

A tremendous portion of the truck market are people who live in urban to suburban areas and need to move things. For that audience, the ability to fit a 4x8' plywood sheet easily puts this ahead of a surprising number of conventional trucks on utility. The 2k lbs payload on the 2WD drive model is more than a Tacoma and some configurations of the F150, for example, popular models that also don't fit a 4x8 sheet without strapping it down over the cab or another awkward technique. It also lists a towing cap of 6,600 which is competitive with many production pickups.

There's a divide in needs between off-roading and moving things around, and this seems oriented in the moving things around direction. I can easily see it working for a landscaper in a suburban environment, for example, where the driving miles per day are really not that high and 6,600 is plenty for a typical landscaper's trailer.

From everything I've seen, true off-roading applications are a pretty small portion of the overall truck market, and one that many popular trucks right now are also poorly optimized for (popular 2WD configurations, middling clearances, etc).

You don't usually have to call any more, there's a captive portal provisioning process. It's not totally reliable and sometimes you might give up after a few tries and call instead.

It's an interesting comment, it has the same "compliment the OP, elaborate, raise a further question" format I've seen used by apparently LLM-generated spam accounts on HN. But, the second paragraph is so incoherently structured that I have a hard time thinking an LLM produces it.

Silent films were inconsistent on frame rate, especially early on. The cameras were hand cranked and so the frame rate was determined by the operator. It wasn't unusual to speed up and slow down the frame rate within a scene to achieve a desired effect. The person cranking the projector, in the early days, had to make a similar judgment. As hand cranked projectors have way to electrically powered ones, handling abnormal speeds became difficult, which lead to standardization. Early silent films almost always run too fast when projected on modern projectors. As a result, variable speed has always been a desirable feature for projectors used for historic films. Film preservationists would often modify projectors to provide it.

It can similarly be very difficult to find aperture masks to fit the unusual aspect ratios of older films, so a projectionist might have to fabricate one. Fortunately that's pretty easy with a file.

I wrote an article about this almost a year and a half ago, and I was wondering how it's held up. I think Scientific American is remiss in not digging a bit deeper, because to me one of the main parts of this story is a commercial phenomenon - street lighting in the US is pretty monopolized, almost all municipal street lights and a good portion of area lights are made by the same company (Acuity). That makes it a lot less surprising that they would exhibit a similar failure around the same time.

Acuity has acknowledged a phosphor defect in their lights and had launched a major warranty repair campaign, but I'm not sure how well that's gone given that new failures are still occurring. At least a year ago, they were struggling with the scale of the problem: it just takes a long time to schedule replacement of failed fixtures when there are so many of them.

I agree that the article text could be clearer. As I understand it, it was originally incorporated as Multiscreen Corporation (probably to work on some kind of multi-projector format which were in vogue at the time) and then renamed to IMAX Corporation after the success of the IMAX system at the 1970 Expo.

This is definitely an area for debate. I've seen the physical resolution of a 70/15 film frame estimated at 70MP, which is obviously a lot more than the ~8MP of 4k. The MP comparisons between film and digital are a little iffy though, and digital ought to be sharper within the limitations of that resolution than film. Ultimately it comes down to marketing but, having not had a direct comparison, I would still expect 70mm to look better than a digital projection system.

I think that digital LED domes might beat film because of the excellent light output and color reproduction, but I guess I'll have to shell out for the Sphere to find out as there are very few of that size.

Thanks! email to me@computer.rip should work, sorry if it has given you trouble. Theater organs are one of my weird little interests, so maybe it's a leap but when I saw a tangential mention that Preston Fleet had been a theater organist some of the dramatic design features of many Omnimax theaters (like the glass-walled projection rooms and displaying the speakers in the preshow) made more sense to me. They're similar to the way many theater organs were installed, especially as they started to become such a niche instrument.

I think you're right, I mixed up some different locations. Here's the cool thing: while I was checking that against newspaper archives I happened to run across an older version of an illustration I saw used in the '90s, but the older version has a more complete caption! It confirms that the Science Museum of Minnesota installation was at least planned to have a Spitz STS like the Fleet. I'll see if I can tell if it was ever installed or not. I've been unsure of whether or not the Fleet was the only example of a combined Omnimax/planetarium.

The same illustration appeared with announcements of some other Omnimax theaters, but I suspect it had just been copied from the Minnesota design without paying much attention. The captions never mention the STS.

However, the side control booth located about halfway up the house, which is present in all of the Omnimax theaters where I've been able to check, is labeled as the "Planetarium console." This could explain the curiosity of the '90s Omnimax theaters having two different control booths. It seems odd to keep that feature without the planetarium projector.

Modern speed control technology has expanded the incline range for steel-wheeled trains quite a bit. Inclines that would have historically pointed towards rubber-tired or non-traction systems are usually within the range of steel wheels with solid-state motor control. Basically the control of torque is much finer than in old resistance-box parallel/series speed controllers, so you can avoid slippage much more easily.

the constant-current drivers in LED lighting are a very different concept from constant-current lighting circuits, which are a ~1920s technology rarely seen today. constant-current lighting circuits can be miles long, operate at up to 1kV or so, and require some type of cut-out/bypass feature at each individual light so that a failure of a single bulb does not take the entire circuit out. The problems that constant-current lighting circuits address (maximizing the life of incandescent bulbs) are all solved in different, more robust ways in modern lighting systems. Most significantly, the carbon-disc cutouts that were the direct cause of the street lighting failures are no longer used (even in legacy constant-current lighting systems, where they have been replaced with more modern devices).

It should be understood that the largest impact of the Starfish Prime test, knocking out streetlights, was the result of a very specific design detail of the street lights that is now quite antiquated (they were high-voltage, constant-current loops with carbon disc arc-over cutouts, and the EMP seems to have caused some combination of direct induced voltage and disregulation of the constant current power supply that bridged the carbon disks). The required repair was replacement of the carbon disks, which is a routine maintenance item for that type of system but of course one that had to be done on an unusually large scale that morning. The same problem would not occur today, as constant-current lighting circuits have all but disappeared.

In the case of the burglar alarms, it is hard to prove definitively, but a likely cause of the problem was analog motion detectors (mostly ultrasonic and RF in use at the time) which were already notorious for false alarms due to input voltage instability. Once again, modern equipment is probably less vulnerable.

Many of the detailed experiments in EMP safety are not published due to the strategic sensitivity, but the general gist seems to be along these lines: during the early Cold War, e.g. the 1950s, EMP was generally not taken seriously as a military concern. Starfish Prime was one of a few events that changed the prevailing attitude towards EMP (although the link between the disruptions in Honolulu and the Starfish Prime test was considered somewhat speculative at the time and only well understood decades later). This lead to the construction of numerous EMP generators and test facilities by the military, which lead to improvements in hardening techniques, some of which have "flowed down" to consumer electronics because they also improve reliability in consideration of hazards like lightning. The main conclusion of these tests was that the biggest EMP concern is communications equipment, because they tend to have the right combination of sensitive electronics (e.g. amplifiers) and connection to antennas or long leads that will pick up a lot of induced voltage.

The effects of EMP on large-scale infrastructure are very difficult to study, since small-scale tests cannot recreate the whole system. The testing that was performed (mostly taking advantage of atmospheric nuclear testing in Nevada during the 1960s) usually did not find evidence of significant danger. For example, testing with telephone lines found that the existing lightning protection measures were mostly sufficient. But, there has been a long-lingering concern that there are systemic issues (e.g. with the complex systems behavior of electrical grid regulation) that these experiments did not reproduce. Further, solid-state electronics are likely more vulnerable to damage than the higher-voltage equipment of the '60s. Computer modeling has helped to fill this in, but at least in the public sphere, much of the hard research on EMP risks still adds up to a "maybe," with a huge range of possible outcomes.

There's a few different reasons things are more complex, but one interesting wrench to throw in is that audio tones may not be the best way to send DTMF. Many digital telephone networks support out-of-band DTMF where the digits are sent as digital keypress events instead of actual tones (tones are usually still emitted to the user for comfort). There are a few potential benefits but mostly it improves reliability over iffy connections, reducing instances of one press being detected as two due a dropout in the middle, for example. I believe 3GPP has supported out-of-band DTMF for some time but it may not have been common, VoLTE encourages it much more. The other end is always going to have support for traditional in-band DTMF because they don't know what type of connection the caller has, so it's not a fatal problem, but less than ideal to use in-band DTMF when out-of-band DTMF is supported. This type of consideration is one of the reasons that the telephony part of phones is more complicated than you might think.

CDMA networks broadcasted the time (from GPS) in the clear as part of the base station advertisements, so you used to see CDMA used as a precision time source without any kind of subscription required. CDMA equipment required accurate time for TDM coordination. Unfortunately GSM uses a different architecture for synchronization and does not require accurate time at all, so you have to be a subscriber to request time information and even then it is not all that reliable.

The backdating is trivially detectable unless you manage to get the database operations to happen the wrong way around, which is why the whole "holding a packet" thing has to happen. But part of the reason for the blackout period is to account for the possibility of that kind of thing happening anyway.

If you have to fake the issue time by five minutes, then 1) the described method is probably infeasible anyway because the connection to the database will time out while the packet is held for multiple minutes, 2) the ticket issue date and audit date on the database event will vary by at least five minutes which makes it obvious that the ticket was improperly issued.

Battery power on common battery phones (in a common battery phone there isn't actually a battery, the terms here are mostly historic) is required for a carbon transmitter to work and, for DTMF dialing, it's used by some DTMF keypads. But battery isn't actually that important to most modern phones, which use ADC/DAC instead of an analog audio setup. Modems are similar, they have their own audio electronics that rely on their external power source. That's a good practice in general because battery power on phone lines is pretty variable and not always very clean, so you don't want to run ICs off of it if you can avoid it. The current is also too limited to use it for much, even indicator lights will run into certification problems.

The issue with the USB modems might actually be a bit different... more frequent use of single-pair digital business telephone systems in the '90s lead to problems with people connecting them to conventional modems. Some of these digital systems used unusually high battery voltages (sort of a PoE-esque method of providing meaningful current to the desk phones for their lights and displays), and there was a concern that they could damage the ADC on modems. So a lot of newer modems actually check the voltage on the line before they connect the audio electronics to it, as a safety precaution. There's an AT response that indicates that the modem is unhappy with the line voltage and I tenuously remember that at least some modems have an AT command to defeat this protection and make them connect anyway. Digital Line Detect is what the feature is usually called, but you might more generally call it a line voltage check.

Most lotteries, all of them that I'm familiar with, blackout ticket sales for several minutes around the draw to avoid order sensitivity issues like this. It's funny, lotto vending machines here don't say when the drawings are for each game, but you can tell by reading the fine print for the five minute window where tickets are not sold.

The current state of HomePlug is weird, the organization behind it dissolved in 2016 and basically dumped the spec on the table (they made it public domain). Since it's closely related to IEEE 1901 it doesn't seem likely that HomePlug will ever "go away," but it's also not going to get better. So I think it's definitely fair to say that G.hn is the replacement, in that it's more actively developed, but HomePlug devices remain plentiful on the market. IME HomePlug devices are more commonly sold in the US than G.hn powerline devices, but I get the impression that things are different in Europe.

the typical "industrial" version of powerline is IEEE 1901, which for example is used by some electrical utilities for SCADA and by some smart meters. The difference can be somewhat academic as many modern powerline protocols are members of the same "family," and IEEE 1901 has two different PHYs that are basically adoptions of HomePlug and HD-PLC (another powerline protocol that I didn't mention because it never really went anywhere with consumers). Some HomePlug devices are certified as interoperable with the HomePlug-derived flavor of IEEE 1901, so sometimes they're literally the same thing.

IEEE 1901 is only specified for 500Mbps though. The more industrial use-cases are rarely high-bandwidth and that market is often pretty satisfied with even Kbps performance, they're just sending Modbus and that sort of thing. IEEE 1901 equipment is also going to be quite a bit more expensive to obtain since the market is small and mostly works on large contracts.

I agree with others that point-to-point wireless is probably your best bet. It can be similarly priced to HomePlug AV2 transceivers and, sort of ironically, will probably turn out to be more reliable. HomePlug tends to have trouble when there are neutral bonds because that adds "side legs" to the bus that harbor reflections. That's why people tell you that, as a rule of thumb, your transceivers need to be on the same circuit for good performance. It's a particularly bad with an outbuilding scenario because you've probably got two panels with two neutral buses, adding two different sets of reflections. Hard for the modulation scheme to contend with. I've personally run HomePlug AV1 from a house to a pump shed with a subpanel and got ~15Mbps performance with near-total dropout when the pump was running. ymmv depending on the wiring.

You might also consider direct-burial Ethernet, which is not very expensive. However, you'll get into some complexities with bonding and lightning protection and you might need to study the code book a bit. Some people will insist that one must never connect separate buildings with metallic communications conductors, but I would remind them that until about the 1980s that was the only way to do it, and techniques and equipment to do it safely have been developed. You just have to, you know, learn and use them.

There are commercial machines, but it's important to understand that in the textile industry there's a big difference between commercial and domestic machines, and it's not necessarily that commercial machines are better.

Besides the enormous price difference, commercial machines are usually less flexible than domestic machines. They're optimized to perform a single task at production volume, rather than to do a variety of tasks. Much like how commercial sewing machines typically perform only a single stitch (as opposed to domestic machines, of which modern examples can perform an arbitrary number under computer control), commercial knitting machines can usually only perform a single type of knit. This does mean that the decline of domestic machines in some parts of the textile industry leads to a loss of capabilities that used to be available.

I don't think licensure is really that much of a barrier, though. One of the huge trends going on is that nurses are increasingly replacing doctors in primary care. In my market it's unusual to have an actual doctor as a primary care provider. These nurses just go through some additional training for a PA or NP license and it's still a great deal cheaper than medical school.

There's a couple reasons that I know of, plus I suspect it may be cheaper for the manufacturer. One is that the media type selection in the printer driver (especially glossy vs. matte) changes the ink composition used for black, and you wouldn't have the ability to adjust that if it was premixed. Another is that "automatic" use of color inks for black is an RGB thing; when printing CMYK the same thing is done but it's actually part of the original data. That is, a "deep" black in a CMYK image will have non-zero CMY. Another way to put this is that the whole "we have to use color ink to produce black" is basically an artifact of a mapping problem between how RGB additive-color and CMYK subtractive-color look for black. If you prepare a CMYK graphic you can put down a sample of "100% black" or CMYK 0,0,0,100 and whatever your editing tool considers "black," like CMYK 60,40,40,100, and you'll find that they look quite different printed. But people working in the CMYK space expect to be able to control that to their preferences; people printing documents get it done automatically as a convenience.

Photo-quality inkjet printers sometimes use two different black cartridges, I'm not sure what exactly goes into the composition of the two. Art reproduction inkjet printers (giclee) can use 10, 11, even 12 different pigments to get optimum reproduction across the whole gamut. It gets very technical.

There's a couple of problems with the theory.

First, the reason inkjet printers use color ink for monochrome documents is pretty well known. While there is no doubt a degree of "profit optimization," there's a printing benefit to doing so. Most inkjet printers, because of the properties of the ink used, cannot produce very good blacks with only their black ink. It's standard to use some magenta and blue to 'deepen' the black which produces a subjectively better result. On many printers you can toggle this off, either on the printer or in the print driver. But, and here's where the profit optimization comes back, on a lot of cheaper printers especially you can't (although this might have more to do with the general lack of configurability of inexpensive printers). This technique is unnecessary for laser printers because of their different properties (toner is an opaque material bonded to the surface of the paper; ink is a liquid with a degree of transparency that is absorbed by the paper).

There's also an argument made by inkjet manufacturers that cycling the color cartridge is important to keeping the print head ready for use, although I don't think it's really that big of a motive since with some firmware work they could just run the cleaning cycle on the color cartridge for each print job (although, once again, a lot of this comes down to cheap printers being built around commodity controllers with very little configurability or intelligence in general).

Second, MIC-type dot markings are associated only with laser printers. The concept was developed within the laser printer industry and does not work as well on inkjets due to the higher level of bleed and poorer halftoning of very faint colors. I am not aware of any inkjet printers that print these types of dots; I would not be surprised to learn that there are a handful (particularly in the higher-end photographic market) but it's certainly not common. The EFF, for example, says that no inkjet printers do so. There's probably not much value to printing tracking dots anyway, because inkjet output is usually more obviously different from offset printing than laser (poorer color saturation and density), which makes inkjets unappealing for counterfeiting. There are, of course, a whole different class of "giclee" printers with excellent output quality (is HP Indigo still king?) but they're specialty devices and tracking dots only appear on consumer and office equipment.

Honestly a lot of those recordings probably do sound a lot worse than the radio audio. I rarely see YouTube recordings that are as audible as the radio is in person. Here's what seems to be the reason:

The common splitters you can buy to break out your headset connector to a recorder don't account for the signal level, which is very high on the headset connectors as aviation headsets are traditionally pretty high impedance. I've struggled with the headset audio blowing out even a fairly nice recorder (a Zoom) with the gain turned all the way down. Phones and pocket reporters don't even offer a gain adjustment and the recording can end up almost unusable. In a lot of YouTube videos of pilots, even most, it's pretty obvious that it's clipping at the recorder the whole time. Perhaps even worse, a lot of people are using like a GoPro with auto-gain, so you get the worst of both worlds: it ramps up gain until the noise is loud, and then when someone starts talking, it ramps down the gain, but a little too slowly, and it's still clipping even when it hits minimum.

It's not very common to have trouble understanding the controller when in the air. AM radio at line of sight (as is the case when you're flying) is pretty robust. Maybe the hardest thing to understand are helicopter pilots because there's often rotor noise on their end.

I'm sure this depends on where you live, but my Amazon shipments are late such a large portion of the time that they end up refunding most of the shipping costs I pay. It's like free prime for the patient!

Flying multi-engine aircraft with an engine shut down is a routine training and test maneuver, so these aircraft have all been flown a lot of hours with an engine out. The tricky thing about ETOPS is ensuring very high engine reliability (so that the probability of coincidentally having two engines fail on a flight is low) and avoiding failure modes that would affect both engines at once (one of the reasons for a lot of redundancy in electrical systems).

And while technically different rules, ETOPS in practice gets attached to other requirements for transoceanic flights, so ETOPS aircraft often have additional life rafts and other equipment.