ADSL, being essentially a form of alternating current, will pass through an air gap. I was enlightened on this by an AT&T tech who pointed out that one of my ADSL lines had several breaks and could not carry DC but the ADSL signal still came through. The other line was dead so I was running essentially on one wire with an earth ground. Here is an interesting discussion:
> Anyway, my hat is off to the people who designed and implemented ADSL.
It's a blessing-and-a-curse: too many incumbent ISPs in highly-developed nations used ADSL's ability to run on anything as an excuse to put-off FTTH deployments (looking at you, BT).
I think we (in Stamford Lincolnshire, UK) must be pretty unique right now with TWO competing FTTP startups both rolling out on the same streets. One day you will see Lightspeed Broadband pulling their fibre through the BT ducts and putting boxes on the top of telegraph polls. The next day Upp Brordband will be on the same street. So bizarre they they are doing the same town!
Apparently we are due to have BT put in their own fibre in the next few months too. Really don’t understand why they are doubling up the infrastructure.
Basically there is an enormous amount of capital (at least £10bn from startup providers) out there going into UK FTTH builds. BT focussed too much of content (BT Sport) instead of FTTH and private equity now thinks there is an opp to steal marketshare from BT/VM.
However BT have now now committed £10-20bn, VM probably a few billion.
Thanks, I figured it was something like that. One of the startups here is a bunch of former BT execs so I was assuming they were hoping to exit by selling either to BT or VM.
Very strange! Mine was not quite as happy a story, but here in Silicon Valley (1mi from Facebook) I got a local ISP announcing fiber, and the very next week AT&T was running their own lines. This was back in 2019, and it felt like "everyone" had fiber before we did. 2 years later I guess it feels like old hat. And the local ISP has not yet run the fiber they promised. But one fast ISP is better than zero!
Good luck with your deployment. I'm still so happy about it.
Your incumbent killed the local ISP's project. Fibre customers generally won't change ISPs in the first 2-3 years of having service, so being undercut by the incumbent makes it worthless to continue with the cost of construction when you'll only get a handful of customers. I know because the incumbent has done exactly the same thing to me. A project that planned on having 140 customers can't be supported by 5.
I had a chuckle at the 3.5Mbps that the wet string was getting in the article. When I first moved in to this house, I was getting around 3Mbps on ADSL. Thankfully now I'm on 100Mbps fibre (not amazing by global standards, but good by Australian standards).
That wet string would have been an upgrade for me.
From previous personal experience in building new plants, and expanding existing plants: Cost of deployment and slow roi are the primary drivers of stagnating local networks.
Complicated corporate accounting, carrier incumbency, and weak governments are the core causes. Carriers being publicly traded companies really screws up incentives to fix these problems. It seems to be mostly a binary decision at the top; more profit or better service?
also, the infra (which ADSL runs on) was build in a time when telephone companies used to be either state-owned or a single monopoly with heavy goverment involvement.
Doing the same thing with fiber is necessary, but will not happen without strong govermental involvement.
Indeed. New Zealand has had a pretty successful fiber roll out over the last several years because the government awarded exclusive contracts to fiber providers that then have to provide access to their network to all ISPs.
Works great. Even my village of several hundred people has fiber now.
No, because 5g is a shared medium. It can deliver... 3 gigabit/s? or something like that? Let's say it's 10Gb. That's 10gb shared with everyone in the vicinity, which is not great especially in high density areas like apartment buildings.
Furthermore, you still need to run fiber to the actual base stations anyway.
Personally I am yes, but I know that's not the case everywhere. I get that you mean in terms of ROI, but that's ROI for the business, not for you the customer. So I guess what I'm getting at is, why would you suggest the thing that's better for the business but worse for you?
Because it’s not worse for me, it’s the same cost and value. To the other point, companies outside monopolies and prestige add a margin, if they do it cheaper it flows to the consumer, a company isn’t going to have low fiber margin if they can have better 5g margin, but I suppose the proof is in the pudding (and government incentives)
>>...*my hat is off to the people who designed and implemented ADSL.*
Maybe a few will recall: San Jose California, in the epicenter of Silicon Valley -- but for some reason Comcast (was previously called *COVID*) -- and you couldnt get DSL in San Jose at the time .... literally down the street from Netflix, and freaking home DSL took YEARS for it to reach our houses...
(My point is that it was ironic that in the heart of silicon valley we couldnt even get DSL due to COVID/Comcast
Are you thinking of COVAD? IIRC, they were a competitive local exchange carrier, unrelated to Comcast.
As a CLEC, they could place DSL equipment in the incumbent carriers (mostly Pacific Bell/ATT, but Los Gatos Telephone company was absorbed by GTE/Verizon and I think sold to Frontier) and use the existing wiring to run DSL. In silicon valley, this doesn't offer great coverage; to get reasonable line lengths, you need to be in the telephone company's remote terminals and that's not available to CLECs.
I was one of two providers in their 13 state region that used it. It was really successful and let us put in ADSL and then Ethernet over Copper in business parks.
In some sense, that's "just" radio. An antenna is a wire... it's sending a signal and picking it up from a very nearby antenna. Radio transmissions are all AC.
(Arguably, the real insight here is that the very existence of radio is impressive / unintuitive.)
this explains a problem i had in Ireland... ADSL worked, but phone line had to dial tone... engineer had no idea how it was working... mind you, ISP had sent him out to get better internet... i was on 8mb and was promised closer to 24... after he "fixed" it, it went to 6... so they were really not happy with the "engineer" when i canceled 2 days later...
Its DC. If you had to imagine it, think of it as a range of radio stations being broadcast down a wire instead of over the air and your router can tune in to all the radio stations at the same time and then piece together the different bits of data being broadcast.
Long Wave would be ADSL, ADSL2, Medium Wave ADSL2+, and FM would be higher forms of ADSL to give you your 40Mb, 80Mb, 100Mb download speeds.
With this broadcasting of signals down a wire now known, it becomes somewhat unsurprising anything capable of transmitting an electrical voltage & current would be capable of transmitting ADSL. Not knocking their effort though, Arnold and Arnold have always like to demonstrate their knowledge. One of them has a personal blog which can be quite interesting.
I wonder if they have considered trying to adapt an SDR dongle to become an ADSL transmitter?
The telephone cable coming into the house is 50volts DC is not AC like a powerline. I know radio waves are just that, waves, its how things like noise cancelling headphones work. Different frequency's give you different ranges or distances for 1 watt, which is why you can bounce Long wave around the planet.
Radio waves down a wire are by definition AC. Otherwise they don't work. The voltage must change, thus the current must change, thus it is AC. Just because it's not 50/60Hz AC like a powerline doesn't change that.
There might be a DC component, but ultimately all the ADSL modem cares about is the AC part.
Couldn't you send an amplitude modulated signal down a DC line by modulating the voltage but keeping that voltage always above zero? If the current never actually reverses, it wouldn't be AC as I understand it. It would be PDC, pulsed direct current.
I wasnt taught that radio waves were to be considered identical to AC power down a cable but when thinking about it, they probably are identical with waveform properties and the difference being the medium they are travelling through.
The exact details become confusing and get into some physics details, but in practice radio frequency on a cable is basically an AC voltage that needs special care to not be lost to inductance and other effects. This is of course part of the general trend that DC through gamma radiation are in many ways the same thing.
It's common parlance to say "DC component" to refer to any offset from zero in the AC waveform. So, for example, a typical analog telephone line when in use could be described as having a DC component of around 5 volts (referred to as the battery voltage for historic reasons), and then an AC component of around a few volts (varying by signal amplitude) is superimposed. Someone else mentioned the case of an AC signal with its center point not at zero actually being a pulsed DC signal... but both are correct in their own ways. An AC signal with a DC component will have its "neutral" voltage wherever the DC component puts it. This isn't usually referred to as pulsed DC because the AC signal usually starts out that way---as AC, and the DC component gets added. To receive the signal, the DC component is essentially removed. A lot of real systems end up this way either intentionally (in the case of phones) or unintentionally. Much of the time people talk about a DC component its in the sense of an undesirable one induced for some reason. Many people who use SDRs are familiar with this as common direct-conversion SDRs virtually always pick up a spurious DC voltage in the down-converter used to bring the selected frequency band into the range of the ADC. This results in the so-called "DC spike" in the middle of the tuned band.
Now, others have said, and elsewhere you have probably read, that telephone battery voltage is 48-ish volts (varies somewhat by central office equipment and line loss, phones are expected to tolerate a wide range). That's true, but when a phone is taken off hook it closes the loop (while presenting some resistance) and the voltage drops much lower. One of the odd things about DSL from a telephony perspective is that, unlike normal telephone applications, it is designed to function whether the phone is on or off hook. As a result, DSL devices do not make assumptions about the battery voltage, which during DSL operation can vary from off-hook of a few volts to ringing of around 100 volts.
Another odd detail of telephone circuits is that typical local loops use two wires, one pair, for audio both directions. The telephone, though, needs an "in" and an "out" to connect to the microphone and speaker. Similarly, the telephone network itself predominantly operates using pairs of two separate signal circuits, one for each direction, as this greatly simplified analog telephone systems and is required for digitization for digital ones. This is achieved by the use of a hybrid on each end of the phone line, which historically was a type of matching transformer that used some clever electrical tricks to provide three taps. One has signals both directions, the other two have one of each signal cancelled out based on matching or mismatching the impedance of the telephone line. It's a bit hard to wrap your head around and rather clever. Unfortunately hybrids, being analog devices, are never perfect and introduce some oddities on the line. DSL devices must use DSP methods to contend with phase shifts and other issues caused by hybrids. Today, it is increasingly common for not just telco equipment but also consumer phones to also use DSP instead of a hybrid to isolate the directions, since the DSP can self-tune to achieve a more perfect result. Amusingly, so-called "sidetone" in telephones (being able to hear yourself in the speaker) is an undesired result of imperfect performance of the hybrid but turns out to be an important comfort to humans, so DSP-based systems usually intentionally mix the outbound audio into the inbound at a low level.
All of this adds up to DSL being surprisingly robust. Unfortunately, there is a downside to the fact that DSL relies on frequencies beyond what telephone circuits were originally designed to convey: line loss of DSL signals is very high, which results in a rather short practical range for DSL, typically only a few miles even with a local loop in good condition. DOCSIS is able to achieve tens of miles, even at the very high speeds it supports, because coaxial cable and the fittings and amplifiers used are designed to carry high frequencies with minimal loss. Even so, the push to greater-than-gigabit speeds has required outside plant upgrades for cable networks, just as the push to expand DSL coverage (and less so, but in some markets, speed) has lead to outside plant improvements to the telephone network, such as heavy use of remote DSLAMs that "convert" most of the subscriber loop to a longer-range medium like fiber.
> Amusingly, so-called "sidetone" in telephones (being able to hear yourself in the speaker) is an undesired result of imperfect performance of the hybrid but turns out to be an important comfort to humans, so DSP-based systems usually intentionally mix the outbound audio into the inbound at a low level.
I wonder if the circuit lag from sidetone is something that affects hearing aid users, considering they have another circuit in which audio has to go through before the user gets to hear, but I wonder if the sidetone passes through their skull or jaw bone instead, totally bypassing their hearing aid. I guess the speed of electrical circuits, the speed of electricity passing through a circuit, is a bonus for our slower nervous system and brain which is only running at speeds of up to the old 286's/386's/486's iirc.
>DOCSIS
>coaxial cable and the fittings and amplifiers used are designed to carry high frequencies with minimal loss
So the old Token Ring network never died out it just morphed into Cable networks?
>heavy use of remote DSLAMs that "convert" most of the subscriber loop to a longer-range medium like fiber.
And then there is Deep Packet Analysis (DPA) which can not only be used as a firewall like solution, but also used for compression/decompression to increase the bandwith of fibre by virtue of using compression algo's that give high rates of compression for different types of packet streams based on the type of data and also the way its delivered.
May be Youtube's delivery of packets from a variety of servers in a co-ordinated manner could negatively affect the compression algos, that could then be used to deliver over fibre and other networks, because we cant assume all network traffic for a service comes from one server. At the same time, this method of delivery can also be used to work out where compression of packet data is taking place on a "hop" or number of hops on the network to the end user, by virtue of packets arriving out of order. I think that method could be used to work out physical layouts of telephone networks between their servers and the end user. I then wonder are the spooks/telco providers in some country's using crypto currency like "tumblers" to make the telephone network change so no route is ever the same.
Its interesting but frustrating when looking back at some of the ways things were explained when at school, education can be used for so much more intelligence gathering than meets the eye.
The reason for your confusion is that the telephone exchange sends a constant Current, not a constant Voltage. There is 48V, but it's behind a 300+300Ohm relay which limits the current.
More the reason that I said it varies is because it depends on the equipment. In the US it is nominally derived from 24x lead-acid cells yielding 48v, but in older switches the maintenance charger is connected when the switch has external power and increases battery voltage to around 50v, sometimes a bit higher, like 54v. Basically due to the charger, other countries often specify 50v as the nominal voltage (this is of course similar to how we call automotive systems 12v when in practice they're around 13.7v most of the time).
All this results in 40-50v being considered a normal on-hook line voltage, but it can vary more in the real world. Of course modern SAIs or RLCs or what have you tend to use solid-state regulators that keep a very tight 48v, so I'm sure the variation is much lower in like modern suburban neighborhoods than it is in cities or with older exchanges.
When off-hook, current starts flowing and the line relays and local loop come into play. The line relays are not tightly standardized and range from say 400-700 ohm, but unless you're pretty close to the exchange the line resistance of the local loop is greater, which can be 1kohm or more. Then the actual telephone instrument has a resistance due to the current it uses for operation, 200 ohm is perhaps average but it varies plenty, I think the WECo phones were usually 180 ohm nominal. Both line resistance and telephone resistance vary widely. A total loop resistance of 2400 ohm could be called a maximum because it allows the phone the 20 mA that's considered a minimum for reliable telephone operation, but lots of equipment will work out of that range, especially since so many newer phones have an independent power supply and digital voice circuit. On older switches, where "older" includes plenty that are still in wide service like 5ESS, the line cards have a couple of jumper options to adjust the relay resistance in order to bring loop current up or down depending on length of the loop. That's mostly because high loop currents due to a short loop can shorten the service life of equipment.
Nothing is really regulated (on older equipment and per specs, newer equipment tends to have voltage regulation as a result of using more advanced transistorized power supplies), neither voltage nor current, and so it can all vary within a fairly wide range. This is surprising from the modern perspective but not so much when you consider that the "standards" here are a hundred years old. Newer switches, RLCs, etc often measure the current on lines and raise trouble alarms when it's too high or low, which does impose certain tighter bounds.
That fact that this delivers 3.5 MBit/s really makes you wonder how many low speed connections out in the wild are literally broken cables that still have some amount of coupling somewhere.
I lived in a forested area as a kid and the copper wire was always breaking for various reasons (falling branches, old deployment, temperature and humidity, etc). The ISP would always attempt to reduce the speed and leave it at that. It took a lot of effort as well as personally locating the breakage to get them to come and repair it properly (and it still took forever).
Potentially apocryphal, but Telstra's copper cable network supposedly had its insulation made of paper, not rubber. I remember when it rained the curbside pits fill with water, causing slowdowns and frequent ADSL dropouts (until things dried out).
It took over a year for Ziply to repair the land line of my 90-year-old parents. 30+ hours on the phone with support, multiple visits by techs who were simply not interested in doing any work. I had a tech tell me, literally to my face, "this line is working fine" when the line was stone dead. Another told me that I had to buy all new phones because the ones my parents had were "out of date". (To humor him, I bought a $15 phone from a local electronics store, plugged it in and showed the tech that it wasn't working. He did nothing).
I have now learned that the WA state utilities commission is pretty interested when providers try to pull stunts like this. You can also dig out useful company contact information from the commission's website.
> I have now learned that the WA state utilities commission is pretty interested when providers try to pull stunts like this.
A number of years ago I worked at a CLEC, during that short window of time when they could exist. One of the more useful things I learned is how much power the PUC has. Every phone company has a team that deals with complaints coming in via the PUC and they are eager to resolve them. Not something I'd necessarily use in lieu of regular old customer service for most issues, but when the first and second attempts fail, calling the PUC will work 100% of the time.
I think this is common in places where they don't expect moisture to reach, but then things change and it gets there anyway.
If your POTS lines are down and the telecom company is telling you a "wet pulp repair" is underway, your phones are going to be down for a while because a bunch of paper-insulated cables need to be manually rewired because they got wet and corroded.
I know there are some telecom folks on here that may be provoked to correct me but pulp was standard before the advent of cheap plastic insulation in the 1950s on up. I live in the midwest and my brother is a lineman for AT&T. There is an astonishing amount of pulp-insulated phone line still in service today.
In order to keep it dry, the conduit that the pulp lines are run through is pressurized to 5-10psi. Anyone that has worked with air compressors knows that pumping ambient pressurized air down into underground pipes is a recipe for condensation, so high capacity air driers are required to remove the water before it goes underground.
Any kind of outage on the compressor or dryer is effectively an emergency because water infiltration can happen almost immediately, creating an outage and extremely expensive repair.
> I know there are some telecom folks on here that may be provoked to correct me
Aka Cunningham’s law
> Any kind of outage on the compressor or dryer
I’m confused: isn’t a bigger concern any physical damage to the conduit anywhere in the run that is too large for the compressor to overcome? Or are we talking football-field-sized compressors here?
The more you learn about this ancient cable technology the more absurd it becomes. We shower these fuckers with money but they would rather keep their paper insulated phone lines with permanent compressors and dryer running than braindead simple fiber. No wonder it is permanently broken and they can't keep a single 9 of reliability.
Fiber may be simple, but the way we use it is not. Unlike copper, a GPON fiber install is going to have active electronics and splice trays for every several dozen subscribers.
Plenty of opportunities for water ingress to still cause problems.
Also, sending a singal across fiber is definitely not easy.
ADSL is basically modulating a radio wave over a cable directly to another device.
Fiber requires high quality optics, high quality lasers, tons of active hardware if you want to do it at scale. (not to mention the mind boggling physics and manufacturing required for things like DWDM, optical path switching etc).
Fiber optics have existed since the 80's yes, but prices of high quality fiber solutions have only dropped massively in the last decade or so.
Exactly. That all sounds infinitely easier than buried air pipes. Mind boggling physics are what gives us CPUs, but the final product is reliable bar none.
yes, but this does not scale if you want to build residential connectivity.
GPON makes this scalable and affordable, but at the cost of technical complexity.
Fiber (as in, the cables themselves) is far cheaper to produce compared to copper, but this has mostly to do with the price of copper and not manufacturing techniques.
Don't go for GPON, if you have a chance.
Direct cabinet-to-apartment single-mode fiber (can be a pair that gets BiDi optics if one of the fibers fails, though only worth it if correlated failures aren't the bulk of issues) is future-proof.
Also GPON tends to not get anywhere near the awesome pings 1G-LR and 10G-LR provide in sub-lightpseed regional situations.
It depends on the country, but originally our Telephone Companies were motivated by Quality of Service. However all that changed when the companies were privatised and profits became their only concern.
Historically there was a continuous upgrade of equipment as the technology improved. Manual exchanges became automatic, step-by-step gave way to cross-bar which gave way to electronic exchanges. Analog phones were replaced with digital and ADSL. And had that steady improvement continued, ADSL would have routinely been replaced with Optical fiber.
What stopped the perpetual upgrades was the arrival Thatcher/Regan/Howard and the advent of Neoliberalism. Which meant that anything which provided a Public Service (gasp Socialism!) was completely abandoned. We are only now starting to realise the long term cost of their vandalism.
There is still a lot of it in service. Sometimes you'll see a tank of nitrogen chained to a pole. It is there to put pressure through the cable to keep water out of a cut/nick on the lead sheath. The lines are pressurized normally from the central office and if the monitoring shows a drop in pressure (a cut in the sheath), they roll out cable maintenance.
Many parts of rural Prince Edward Island (PEI) has DSL running on a phone system that’s probably original from modernization initiatives in the 1960s - 1980s. Party lines were the norm in some areas up west until late-1980s.
Back when a whole family had the same number and you had to ask whoever answered that you want to talk to so and so. Now days everybody has their own number and with caller id you (sometimes) know who is calling.
My daughter is gonna grow up not knowing any of the “shared phone line” etiquette because it is largely obsolete.
The party lines I’m talking about are shared loops between a group of residents in a rural area.
Some of the first-hand accounts I’ve read talked about neighbours listening in on conversations. People could tell a snooper was on the line because the volume of the other caller would drop. There was a social aspect to the whole enterprise because you could tell the one nosy neighbour to get off the line and the volume would magically raise.
Front door etiquette still works basically the same way. A doorbell rings and the whole house hears it. Once person goes to answer it, then passes off the conversation to whoever it's actually for.
This not strictly true: The original pairs were paper insulated, but they were enclosed in a lead sheath which prevented water entry. Plus the cable was pressurised with dry nitrogen to keep out any water. Plus the flow of Nitrogen was monitored so that any pinholes could be detected before they caused a problem. Of course when Telecom was privatised all these quality control issues went out the window.
But there's a further point, the problem with moisture in the lines is the corrosion caused by electrolysis, which in turn is caused by the 50V DC on the lines. So even with modern plastic insulation, the copper would be corroded away by any electrolysis.
One last point: Rubber was almost never used as an insulator on phone lines.
Sums up my youth on ADSL in the hills of LA. Couldn't get a static IP address on coax/cable so I convinced my family to pay out the ears for speakeasy.net DSL w/ a static IP. Performance was terrible!
I had a bonded DSL line for a while when I lived in the Bay Area with service coming from two different twisted pair lines. One line was consistently ~18Mbps, the other barely 3-5. It was pretty clear that one of the pairs was good and the other was broken somewhere alone the way. The lines were all in a bundle, with no way to discern what was what any individual strand was in the bundle (or which was broken or shorted). No one had any motivation to find the break and repair it. And because the line was technically “working”, ATT wouldn’t move it to a different pair. Sonic was the ISP with ATT handling the physical lines.
You can do time domain reflectometry to find out where the breaks, sharp corners and reflections are in the cable.
Some modems have special debug modes in that can do this too - then you get to know exactly how many meters along the wire the break is. When you get close, you can hook a resistor to the line and rerun the test and it'll tell you how many meters forward or back you need to go to find the issue.
Yeah, this was in a neighborhood bundle with many… many lines together. No one was going to dig into that to find which line a mouse or squirrel had chewed the insulation off of. I remember running a few diagnostics, but as it was “working”, no one was going to try to fix it. The ISP couldn’t even convince ATT to move the bad line to a different pair. Which was sad. I was supposed to be in the 40Mbps range, but could only get ~18-20. Also — this was enough bandwidth for us at the time, so I just ran off of the single line and was good. Given some of the dsl horror stories, we weren’t too and off.
Came here to make the same joke. Sure it isn't an insightful comment worthy of great praise. But consider my hat tipped to you.
3.5mb down is faster than my mother used to get from her farm north-west of Kempsey NSW. Though to be fair to Telstra she lived about 30km from the nearest town not 2m like the length of wet string.
When I lived in Perth about a decade ago, I had a DSL line from an exchange about 3-ish km away. If I remember correctly, I got 512kbps down, and 56k modem speeds up.
This was not outer-whoop-whoop either. Metro Perth.
There are IEEE standards for single-pair Ethernet:
> In addition to the more computer-oriented two and four-pair variants, the 10BASE-T1,[17] 100BASE-T1[18] and 1000BASE-T1[19] single-pair Ethernet physical layers are intended for industrial and automotive applications[20] or as optional data channels in other interconnect applications.[21] The single pair operates at full duplex and has a maximum reach of 15 m or 49 ft (100BASE-T1, 1000BASE-T1 link segment type A) or up to 40 m or 130 ft (1000BASE-T1 link segment type B) with up to four in-line connectors. Both physical layers require a balanced twisted pair with an impedance of 100 Ω. The cable must be capable of transmitting 600 MHz for 1000BASE-T1 and 66 MHz for 100BASE-T1. 2.5 Gb/s, 5 Gb/s, and 10 Gb/s over a 15 m single pair is standardized in 802.3ch-2020.[22] As of 2021, the P802.3cy Task Force is examining having 25, 50, 100 Gb/s speeds at lengths up to 11 m.[23]
> The IEEE 802.3bu-2016[12] amendment introduced single-pair Power over Data Lines (PoDL) for the single-pair Ethernet standards 100BASE-T1 and 1000BASE-T1 intended for automotive and industrial applications.[13] On the two-pair or four-pair standards, power is transmitted only between pairs, so that within each pair there is no voltage present other than that representing the transmitted data. With single-pair Ethernet, power is transmitted in parallel to the data. PoDL initially defined ten power classes, ranging from 0.5 to 50 W (at PD).
> Subsequently, PoDL was added to the single-pair variants 10BASE-T1,[14] 2.5GBASE-T1, 5GBASE-T1, and 10GBASE-T1[15] and as of 2021 includes a total of 15 power classes with additional intermediate voltage and power levels.[14]
Sadly, there's not much in the way of equipment for this. I could really use two small 10BaseT-1 to 10BaseT converters, preferably both powered from one end.
Since most of the 1000Base-T1 gear is still unreasonably expensive/effectively impossible to get quickly in small quantities, you can run 100mbps and 1gbps Ethernet over "reasonable" lengths of single twisted pair using MoCA adapters plus coax->twisted pair baluns. Achievable cable length will obviously depend on EMI conditions, but I've had reasonable success with this method on twisted pairs in industrial robots.
GIGA G4201TM modems are built for exactly this, using the G.hn standard, over a single pair. I’ve been using these to avoid digging into walls to replace wiring — they claim to sync at up to 1700mbps and, even in the real world, I’m saturating the 1000BASE-T ports.
For me, I've got a gate with a keypad. It's got an ethernet port, but they only ran 3 pair to it, and it works best with 2 pair for voice communications, so I've only got one pair for data, not enough to use.
That’s funny because my SO’s parents have 1.5Mbps DSL by contract. For only $100/mo they can jump up to 12Mbps. USA and 1 hour from me where I have gigabit docsis 3.1.
If they had 1Mbps because of a fault that would be more unfortunate than unfair.
I remember in the 90s when we were deploying a business campus, we first used ADSL services from the local carrier, but not for long.
We discovered we can get "dry lines", basically just rent copper run from site-to-site, nothing on it from local carrier. Slap ADSL modems on each and we got max throughout, at a fraction of the cost. Then we upgraded to SDSL, and that was like hitting the jackpot.
I’ll go one better, ADSL doesn’t even need two continuous wires to work, one is good enough as long as the other is just barely electrically coupled. I had a 12 month epic journey to get a performance fault fixed on my line. In the end it took 6 technician visits, three senior technicians and finally one smart experienced technician to check the “not in the textbook” faults for a performance degradation and he discovered that my line had was actually mis-wired! I had one wire connected to the exchange and another was a barely connected lose joint (actually disconnected but still technically in the plastic joint housing) about half way to the exchange. I was still getting a few megabits with intermittent drop outs for months on what amounted to a single wire!
To give it a fair shot, assume the driver and microphone are studio quality rather than the kind you’d find on a 1970s telephone handset. I bet it’d work pretty well.
But the real question would then be: how much of an air gap could you create and still get a connection?
Could you post to HN on an ADSL signal that’s being screamed across the length of the room you’re sitting in?
Not sure if this is within the spirit of the question, but: The individual ADSL bands are only 4 kHz wide, so you could modulate 4 or 5 of them down into the audible range (20Hz - 20kHz) and back up again after the transmission through the acoustic coupler. In theory, ADSL should then pick those bands to transmit the data.
The linked article (and government push to do this) completely ignores the fact that this is done frequently now.
It's used to get the last few metres into the home, e.g. from the boundary to the inside of the house. You put a swept tee in at each end, after the stopcock. Water off, dig down adjacent to stopcock, cut pipe, shove a drinking water rated duct down the pipe through the small port on a swept tee. Shove some chlorine tablets in the pipe and couple up to the new swept tee. Repeat interception at other end outside or indoors, and then use standard fibre cable blowing through the inner microduct, and away you go.
There's a huge amount of disused water pipes in most developed nations which are frequently used, similarly using sub-ducting, and you can run cable through mains - but have to come out every time there's a valve, so practically it's usually cheaper to dig. Where it comes in handy is where there's areas you can't practically dig up, e.g. major roads with old pipes underneath.
Source: Have done a bunch of this for a major UK telco.
There is company in Czechia which provides optics via sewage. I guess it is cheaper to use existing infrastructure than to place new pipes under roads.
There used to be a debate about going All-in on GPON or doing FTTX with G.Fast. Now G.Fast is pretty much dead or niche at this point. The end of DSL era. While DOCSIS is still doing well in many places.
The next step would be to mandate fibre cables in all new housing. Along with ONT and Router in one solution.
Better regulation around marketing would go a long ways to begin with. In the UK "fiber" is used as a catch-all term for any kind of internet connection even though in the majority of cases it's just fiber up to a certain point and then either DSL or coax, making it hard for consumers to tell exactly what they're signing up for. Same for bullshit terms such a "superfast" or "ultrafast" instead of actual up/down/latency numbers.
Since seeing this article I've been curious about organic conductors .. apparently most carbohydrates / celluloses are really not good basis for conduction but maybe there are tricks to change that.
Conductive polymers are commonly used these days. Pedot:pss can be engineered expressly this way, but less exotic ones like polyamides can do this too.
That's not exactly correct. Electrons don't flow through wires - there's a one-way flow of the ambient electrons around the wire from the field created.
That video is misleading. Electrons must be relatively loose in their orbitals in order for the electromagnetic field to be established with reasonable strength. This does not mean that electricity is the literal flow of electrons. However, electrons actually do flow at a speed of about 1 mm/min due to the electrostatic field in DC circuits. This is not what’s called electricity but they do flow.
You're confusing the electrons and the electromagnetic fields. The electrons absolutely do migrate through the wires; the electric field does not. P.S. that video appears to have been written to confuse/generate controversy and does a terrible job of actually explaining.
> The electrons absolutely do migrate through the wires;
That’s true. But very slowly in electrical terms. If I remember right the actual electronics in a reasonable circuit I read about was something like 1” per second. The vast majority of work done is an electron shuffle of bouncing into the next one in space.
When you say "work", what do you mean? I get the impression you're talking about a model like there's a long tube full of ball-bearings and when you push one in, one drops out the other end?
That model isn't right; think about a transformer - energy is transferred between conductors that are not physically connected at all.
The idea that electrons "push each other" is misleading and an oversimplification.
Watch the video. Like waves in the ocean, are water molecules pushing each other and making the wave? Or is the wave carrying the molecules with itself? Or both things at the same time?
Well .. they do flow in the conductor, and in particular they flow through silicon junctions or none of the semiconductor physics would make sense, but the energy is carried in the field which is indeed outside the conductor.
But maybe you could have different organic crystalline structures allowing AC currents to flow. Wildly speculating of course.. I was just hoping to tape in forest materials to manufacture low power electric devices :)
If you want to try this at home, keep in mind that powerline is essentially the same thing - you don't necessarily need some DSLAM. Also these things spew so much RF they can frequently pair through thin air, just from radiated emissions.
It works on chickenwire too, VDSL not so much. Back in the day when i installed internet lines customers with mandatory ISP service requirement by the gov with absolute shit outside or inside wiring got ADSL, forward-error-correction magic. VDSL was a lot more sensitive.
In some cases I would be forced to use a cat-5 or even poor quality cat-3 where two pairs are for ethernet , one pair for A/VDSL and the blue pair for voice/POTS (voip to pots converted)
I think this relies on the particular string being a linear time-invariant channel. There is some limit where the string won't react accordingly (at a certain low or high frequency). What is that later phenomenon called, anyone know?
Hmm the author had to use salt water to get it working. Maybe resistance is the limiting factor rather than dispersion. In which case a higher power modem or some sort of amplifier would get this working over >2m distances.
Honestly, any ODFM system is so incredibly resilient they will work over nearly any medium. I've tested powerline ethernet airgapped, and it still faster than the WiFI on the embedded system I was testing.
And that is the problem with Ethernet over Powerline. Because the power lines are not balanced or shielded, most of the RF energy escapes and can cause serious interference to licensed radio services.
And of course, if the interference can get out, it can also get in. Which is why Powerline Ethernet can work just fine one day, then suddenly stop working.
Plus the big problem with any ODFM system is that it is incredibly intolerant of wideband interference, eg a series of sparks. The reason being that the band of ODFM channels are fed straight into an A/D converter without channel filters. So each time that wideband interference takes out the system, the modem has to stop and renegotiate each channel from the start.
To any experienced RF engineer, Ethernet over Powerline (or any ADSL system) is a disaster waiting to happen.
"Phone line with 1 broken wire still gets ADSL2"
https://forums.whirlpool.net.au/archive/9yzp5wr3
Anyway, my hat is off to the people who designed and implemented ADSL.