Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?

Possible uses for Power over Ethernet 385

jsailor writes "Power over Ethernet allows devices to draw power from the Ethernet cable they use for networking. Power is provided by the LAN switch (end-span) or an intermediary device (mid-span). The current spec. is 802.3af and was covered on slashdot before. It provides approximately 13W at the end of a 100 m cable and is commonly used for IP phones, wireless access points, and increasingly security cameras. The technology saves costs associated with running power to the odd locations access points find themselves in and allows IP phones to be moved around with out carrying a power brick. The industry is considering a new standard that would provide up to 39W to a network device. Bizarre uses include electric razors. "
This discussion has been archived. No new comments can be posted.

Possible uses for Power over Ethernet

Comments Filter:
  • by 00null00 ( 530499 ) on Thursday December 16, 2004 @03:47PM (#11108235)
    But isn't it time for power over wi-fi?
    • Re:Easy enough, (Score:2, Insightful)

      Tesla (who worked with Edison on early electric devices) wanted to transmit electricity wirelessly. Edison ruled it out because you couldn't charge for it that way. It's a good thing Edison won out, as to get enough electricity to power anything useful into the air over any real distance would be a huge cancer risk.
      • Wireless Power (Score:3, Interesting)

        by EqualSlash ( 690076 )

        Don't send it in the form of electricty..send it in the form of radiation energy just like how the Sun provides us energy wirelessly. Even NASA tested a Laser-Powered Aircraft [] last year.
      • Re:Easy enough, (Score:3, Insightful)

        by saider ( 177166 )
        It's a good thing Edison won out, as to get enough electricity to power anything useful into the air over any real distance would be a huge cancer risk.

        Please provide some references for this. I did a paper on this topic about 6 years ago and I could not find one study that provided a link between power and radio frequency radiation and cancer.

        What I did find was a lot of people who wanted to blame someone for their ailments. I read several complaints and they all basically read "there were no carcinogen
        • Re:Easy enough, (Score:5, Insightful)

          by timster ( 32400 ) on Thursday December 16, 2004 @04:43PM (#11108896)
          As I recall the whole "power lines cause cancer" thing was an example of irrelevant correlation. Turns out that statistically it tends to be poor people living next to high-voltage power lines and poor people have higher cancer rates for all sorts of other reasons.
      • Re:Easy enough, (Score:5, Informative)

        by the pickle ( 261584 ) on Thursday December 16, 2004 @04:50PM (#11108970) Homepage
        You do realise that RF is nonionising radiation, right? And that *ionising* radiation is required to cause the mutations in DNA that lead to cancer, right?

        Just checking.

    • by xpyr ( 743763 ) on Thursday December 16, 2004 @03:54PM (#11108325) Homepage
      Obligatory bash quote, see bash []

      harm_: today this one lady got pissed off cause we dont carry i quote wireless power supplies
      ogregasm: a what
      harm_: thats what i said
      harm_: maybe you want an adaptor for a wireless router o rsomething??
      harm_: shes goes no no i read online about this i wannit i wannit :harm_: then she got pissed when i told her that kind of technology doesnt exist
      ogregasm: heh :harm_: i tried to be nice but it got to the point where i was like"get back to us in 30 years"
      harm_: "once we attain the secret of positron deflector shields, wireless power supplies shall become a reality"
      ogregasm: why bother being that much of an ass to the poor woman
      harm_: well shes the one who got all up in my face asking for the store manager
      harm_: i told her he had just teleported to a corporate meeting in tokyo

      Ah gotta love bash :)
    • Re:Easy enough, (Score:3, Interesting)

      by Ignignot ( 782335 )
      This is rated funny, but Nikola Tesla was working on something like this for much of his life. The Wyadcliffe (sp?) tower is just the biggest example. Go check it out on wikipedia [] like you do for everything else.
      • For that matter, everyone doing work on Solar Power Satellites [] would be interested to know that this sort of thing is impossible.
      • The Wyadcliffe (sp?) tower is just the biggest example. Go check it out on wikipedia like you do for everything else.
        From your very own link:
        Wardenclyffe Tower
    • Lower cost per AP (Score:5, Informative)

      by ccbutler ( 840014 ) on Thursday December 16, 2004 @04:22PM (#11108623) Journal
      earlier this year I converted our warehouse of 250,000 square feet to 802.11b WiFi using Cisco 1200 series AP's. Our cost per AP was 1900.00 (CDN) using power over ethernet. This cost includes contractors, electricians, cat5e, fiber, and even antennas. Im not here to toot any horns for 802.11b or Cisco or anything... but our cost per AP would have been WAY higher if it weren't for power-over-ethernet technology.
    • You mean like the B.E.T. []? (It stands for Broadcast Energy Transmitter, but I think it's funnier to think of GI Joe and Cobra battling over control of Black Entertainment Television)
    • So if your box get 0wned the lights go dim?
  • The razor doesn't have networking capabilities!

    • The razor doesn't have networking capabilities!

      I thought a similar thing the first time I saw one of those little laptop lights that plug into the USB port. Now devices that use USB just for power are extremely common and some are quite creative and useful. I love recharging my cell phone with a a USB cable because I dont' need an extra brick(transformer) to get the job done.

      In fact, even though power over Ethernet is a great idea, I'll bet it's biggest competitor will continue to be good ol' USB. The
      • Powering many common devices using USB, Ethernet, or other low voltage sources makes a lot of sense. Many devices that are in widespread use such as battery chargers, small lights, telephones, inkjet printers, do not need the full 120/240 volts to operate. Low voltage power could be a lot more convenient in many cases, since a standard electrical outlet and the transformer plug would not be required.
  • by oGMo ( 379 )

    Now if I could have my PDA draw power from the wifi card, I wouldn't even need a battery!

  • Gigabit ethernet? (Score:3, Interesting)

    by mgs1000 ( 583340 ) on Thursday December 16, 2004 @03:49PM (#11108257) Journal
    I guess it won't be compatible with gigabit over cat5e, since that uses all eight wires.
    • I sure hope your job isn't soothsayer.

      There is no fundamental reason that DC power-pass could not be made to work with Gig-E, just as a single pair can simultaneously carry RF, DC power, and a tuning voltage (the feedline to the LNB for a DBS satellite).

    • Re:Gigabit ethernet? (Score:4, Informative)

      by enigmals1 ( 667526 ) on Thursday December 16, 2004 @04:10PM (#11108511)
      Yes you can. The power is running on the same wires as the data. This is roughly the same technology as Broadband Over Power. The power is 60Hz but the data is MHz...or in your case, GHz. Little to no crosstalk.
  • by __aaitqo8496 ( 231556 ) * on Thursday December 16, 2004 @03:49PM (#11108263) Journal
    Power over Ethernet?
    Internet over Powerlines?

    What crazy things will they think of next? Power over powerlines and internet over ethernet?!?
  • the next USB (Score:4, Insightful)

    by wattersa ( 629338 ) <[andrew] [at] []> on Thursday December 16, 2004 @03:50PM (#11108266) Homepage
    I for one would like to have my ethernet hubs use the standard wiring for power rather than a brick and AC adapter that I have to find an outlet for. Since telephones already do this it's just the next step in the direction of USB everything. Which seems to be a good thing (tm). Now I know how to set up a LAN in an unwired munitions bunker...
  •, of course, does that mean I can install linux on my razor?!?!?
    • does that mean I can install linux on my razor?!
      You, probably, will soon be able to, but the project will never get beyond single-user booting.

      Oh, and you'll need proprietory firmware for the blades.

  • by Sheetrock ( 152993 ) on Thursday December 16, 2004 @03:51PM (#11108294) Homepage Journal
    Depending on the voltage and amount of power involved.

    There are a couple of drawbacks to this plan: first, the increased caution that will be necessary in working with network cable (everybody's used to them being safe as phone lines) and second the possibility of burning out devices that weren't built with this standard in mind. Who's to say that a cheapie network extender installed in a rat's nest of cabling five years ago wouldn't start a fire when you hook something like this up?

    • an excellent post. volts [] don't kill people, amperes [] do! and since watts [] are the product of voltage and amperage, and voltage will be likely low... this would lead me to believe that yes, these could be dangerous devices with a good amount of current going through... a physics professor of mine once said "it only takes a single amp to stop your heart"... oh yeah! now we can play flatliners without the need for a power outlet! sweet!
      • by MORTAR_COMBAT! ( 589963 ) on Thursday December 16, 2004 @04:04PM (#11108447)
        well this random post [] seems to claim that 1 mA can kill a sick person, and 100 mA can kill a healthy person... so my "an amp can kill a person" should actually say "an amp could kill 1000 sick people... or 10 healthy people... or some combination thereof..."
      • by Frennzy ( 730093 ) on Thursday December 16, 2004 @04:06PM (#11108476) Homepage
        UL considers the average human (for testing safety purposes) to be about 500 Ohms. Since most PoE is around 12v, you end up with about 24 milliamps across a 500 ohm load.

        For that to have a severely negative effect, it would need to cross your heart. Most of the current will likely go around your skin (you are your own faraday cage) so you most likely would never even feel it.

        Plus, you would have to actually come in contact with it...which is pretty easy to avoid.
        • Is the UL definition for DC current? Or is that 500 ohms impedance, at the 60 Hz US standard line frequency? I wouldn't think 12V DC will hurt anyone (unless it's applied to your tongue, like testing 9V batteries; or if you drop a wrench across your car battery terminals, that might be bad...)

          I had an e-mag lecturer who asserted that 60 Hz was selected as a national standard in part because this frequency worked well for the electric chair. I find this hard to believe, more likely he was trying to be a
          • It's for DC resistance, not AC impedance. ( I used to build energizers for electric fences, and the owner of the company wanted to get UL marked. Unfortunately, the total energy transfer in our design was two orders of magnitude higher than UL would allow for...any less any the fences were ineffective, so we never got UL marked). We used a variety of DC voltage levels, up to about 10k (for Buffalo) with a 17ms pulse. Let me tell you, I got hit more than once..and that stuff *hurt*, but it never killed m
          • by ScrewMaster ( 602015 ) on Thursday December 16, 2004 @09:37PM (#11111793)
            60 Hz. was selected as a national standard because Tesla worked out the numbers and George Westinghouse went along with him, and the rest of the country ended up going along with Westinghouse. Westinghouse was concerned about power transmission and 60 Hz. was selected for efficiency with the generator and transformer technology of the day. Remember Tesla's proficiency with those.

            Your professor is a bit confused about the electric chair business: it was Thomas Edison who claimed publicly that Westinghouse's 60 Hz. system was much more dangerous than Edison's own direct current power system. This was strictly a marketing ploy: he and Westinghouse were going head-to-head in an all out corporate war and Edison wanted to win, badly. He had no scientific basis for his claims. In other words, he lied, publicly and repeatedly. He even went so far as to have a major correctional institution that was building a new electric chair facility install Westinghouse generators in order to "prove" how dangerous alternating current could be. The reality is that Edison was way off base: direct current is substantially more risky than alternating: for example, if you grip a pipe charged with 120 VAC, you will get a nice shock but will be able to release your hold. The jolt might cause your heart to fibrillate but most likely you'll survive. Grab that same pipe with 120 VDC and your muscles will lock and you won't be able to let go ... your heart will also stop dead if the current happens to pass through it. A lot of lives were spared over the years because we didn't go with Edison on that one. The other reason to rejoice is that a DC power distribution system would have required power plants plastered all over the place since transformer operation (and hence high-voltage landline transmission) would have been impossible. Today we could probably do it with high-powered DC-AC inverters, but that technology was way beyond Westinghouse and Edison.

            The only thing that saves us from instant death the first time we walk across a carpeted room in dry weather is our epidermis. That layer of dead tissue makes an excellent electrical insulator. Otherwise, the first static spark you drew touching a doorknob would stop your heart. Remember, the insides of your body are an ionized, highly-conductive mess: a hundred-odd pounds of adulterated salt water. If you stuck a couple of pins in each index finger, and put those pins across a flashlight battery, you would probably die. Your bloodstream would conduct that tiny current flow directly through your heart. But touch those same terminals with the outer layers of your skin intact: no problem.

            And I'm not making this up: if you've ever been in a hospital burn unit, you would see that everything in those rooms is heavily grounded, and extreme precautions are taken against static discharge or any other electrical artifact reaching the patient. It's amazing. I worked in a lab at a major teaching hospital / university for a while, and I noticed that there were these odd metal plates with heavy-duty green leads hanging out of them, sticking out of the walls and floors. I asked, and was told that the lab space was a converted burn unit. People that have had significant areas of their skin burned off are fatally susceptible to even minor electrical discharges.
            • by lars_stefan_axelsson ( 236283 ) on Friday December 17, 2004 @05:02AM (#11114024) Homepage
              Your professor is a bit confused about the electric chair business: it was Thomas Edison who claimed publicly that Westinghouse's 60 Hz. system was much more dangerous than Edison's own direct current power system. This was strictly a marketing ploy: he and Westinghouse were going head-to-head in an all out corporate war and Edison wanted to win, badly. He had no scientific basis for his claims. In other words, he lied, publicly and repeatedly.

              No that's not true. Edison had plenty of data from animal research. He even had a traveling road show that demonstrated (on sheep mostly) that they died when a comparatively much lover AC voltage was applied than when a DC voltage was applied. "You could turn the dial much higher." And it wasn't all sheep, they even electrocuted an elephant in New York (that had been condemed to death for killing its keeper). He even had billboards that said: "Don't use the executioners electricity in your homes!" (or words to that effect).

              AC was indeed used for the first electrocution, suggested by Edison who build the apparatus. Westinghouse wisely refused to sell any equipment but then Edison arranged a purchase in secret and shipped it in unmarked crates to the place of execution. The first electrocution itself was a horrible botched affair, where many of the witnesses fainted from the stench of burning flesh. And the condemed man was first thought to be dead and the steam let out of the engine, only for the officials realising that he was still alive and everyone having to wait for the steam engine to be fire up again.

              Also, your statement that DC is more dangerous than AC is not quite as straightforward as you make it to be. While at higher currents DC does tend to lock the skelettal muscular system more readily than AC; that doesn't in fact kill you as easily as electricity induced teatanus of the heart tends to resolve once the current is removed (hence defibrilation units use of DC), i.e. the heart starts again. AC otoh tends to cause fibrilation of the heart, which won't resolve itself and kill the patient (unless defibliration is available). We're speaking here of 50/60 Hz AC of course, as AC in the ten-kilohertz range or so is practically safe due to skin effects (your skin is a pretty decent conductor as other's have pointed out). Also, AC will also induce tetanus, though I'm not sure about 120V in the common case (Europe being on a 400/230V system. 230V can be enough to 'stick you on the circuit'.)

              The best links I could find was this [] and this []. Note the table half way down on the second page that lists the amperage needed for various effects on the body. I've had a better link before, but I can't find it now.

        • For that to have a severely negative effect, it would need to cross your heart

          Don't forget "and hope to die"
        • Since most PoE is around 12v,

          I am not sure what you are using, but the Linksys POE injector puts 48 volts in, just like the standard says. The Linksys POE splitter converts to 12V but that's only to be compatible with equipment that doesnt have a POE port.

          I have another brand injector that also puts in 48 volts.
      • Too bad you need a lot of volts to drive a lot of ampts through someones body, so you cant seperate them like that.
        (just checked with my multimeter: my slightly sweaty hands have >5kohm from left hand to right hand even if i hold the contacts really tight. So 5V would give a milliamp, no matter if the source could deliver 50A...
      • Remember, while it's the amps that do kill you, you need enough voltage to push the amps across the heart. After all, you can easily hold onto the terminals of a car battery (12 volts, can deliver several hundred amps easily) with no ill effects.

        It's all about Ohm's law: I=E/R (current equals voltage over resistance). Thus, to get 1 amp through a human body with a resistance of just 1000 ohms (which is a very low figure; the human body usually has more resistance fingertip to fingertip), you would need

    • by YankeeInExile ( 577704 ) * on Thursday December 16, 2004 @04:08PM (#11108491) Homepage Journal
      Who's to say that a cheapie network extender installed in a rat's nest of cabling five years ago wouldn't start a fire when you hook something like this up?
      How about the same UL (and their international equivalents) standards that already keep these same devices from catching fire if accidentally connected to telecoms lines.

      Your assertion that ...used to them being safe as phone lines... begs the question*. Phone lines are not intrinsically safe, and the central office can easily provide several watts of power at 90VAC for ringers.

      *Look, ma! Someone on slashdot who knows what 'begs the question' means!

      In the US, at least, to meet Part 68, telephone gear must also handle line-crosses to 600Vac without creating a hazardous situation.

      • How about the same UL (and their international equivalents) standards that already keep these same devices from catching fire if accidentally connected to telecoms lines.

        You are only looking at half the picture. Its not just the UL listing of the device, but its the installation. While the UL listing helps, building codes (at least in the US) also require that a fully licensed electrician install electrical lines. The local building authority also requires multiple inspections (planning, rough-in, final),
    • by dourk ( 60585 ) on Thursday December 16, 2004 @04:10PM (#11108516) Homepage
      You may assume telephones are safe, but the have a ring votage over 40v. Wiring up a the last jack in my house, stripped one of the wires with my teeth just as my buddy called.

      It fucking hurt.

      • Actually, there's a constant DC voltage of ~48v (less by the time it gets to your house). The ring voltage is AC and closer to 100. Yes, it does fucking hurt.
        • Umm no, the voltage is still 48 when it reaches your house, if the line is open-circuit. When you take a phone off-hook, its resistance combined with the resistance of the line causes the voltage measured across the phone to drop. The resistance placed across the line is everything.
      • Used to live in India, where they take a cavalier attitude to wiring of any kind, so everyone gets their fair share of shocks, but none as funny as the time I rang my friend one afternoon, and got an engaged tone. So, I thought nothing of it and rode round there. When I got there he confronted me at the door ...

        "Did you phone me a few minutes ago?"
        "... yeah, why?"
        "I was rewiring my phone! You just gave me a massive shock!" ... haven't been able to stop laughing at that mental image for years since ... I es
      • The distance from the earth to the sun is over 40 million miles.
    • by shoppa ( 464619 ) on Thursday December 16, 2004 @04:20PM (#11108603)
      Dude, that's almost as funny as the guy who built a glass case around a 10K ohm resistor with a sign that reads "DANGER! 10000 ohms!"
    • (everybody's used to them being safe as phone lines)
      Actually, phone lines can give you quite a shock if you touch them while a phone is ringing. (I'm not sure on current, but) the ring signal is given by a total potential difference of 96V across the 2 wires (+48 and -48). I believe regular usage signal is 24V; but I'm not sure on this, because I did an experiment and turned a phone into a portable tone generator by connecting a 9V battery to where the RJ11 plugs in.
    • That's why the devices first _check_ if the other device is a power over ethernet device. I've read the RFC of the standard, and this functionality is already included.
    • by kmahan ( 80459 ) on Thursday December 16, 2004 @05:28PM (#11109394)
      The spec addresses issues like "devices that can't handle it." You just have to RTFS.

      That 13W isn't always there. The device has to be POE enabled. The hub supplying power senses the device. It then measures a resistance across one of the pairs looking for a very specific resistance. That's what specifies IF PoE is wanted, and then there are different current limits you can request. The hub end is required to limit the current supplied and also monitor for faults (and if so disable the power).

      The spec isn't just some yoyo hooking up an ac adapter to a supposedly unused pair and saying "it works.."
  • Short circuit (Score:5, Interesting)

    by totallygeek ( 263191 ) <> on Thursday December 16, 2004 @03:54PM (#11108327) Homepage
    I went to a company that cabled about 100 drops. When certain network items did not work properly, they tried everything to figure out what the problem was. Finally, one device was plugged in and did not work at all. It turns out that the cabling was wired with "just the same colors on one end as the other". The installers actually created an elaborate mapping on paper saying, wire 1: red, red/white, blue, blue/white, brown, brown/white, green/white, green. They would look up each cable on this run sheet before punching down the other end. The device that did not work evidently was not "looked up" correctly, and so there were no valid pairings. If this had been POE, something would have been fried.

    Another company I worked with found out that their cable guys simply wired everything with 2 pairs only. They would punch down 1,2,3,6 and then cut the remaining wires completely. POE wouldn't work there either.

    It is amazing how some companies attempt to save money by getting monkeys to install cables.

    • Re:Short circuit (Score:4, Informative)

      by HaeMaker ( 221642 ) on Thursday December 16, 2004 @04:02PM (#11108422) Homepage
      Actually, the company who only wired two pair can get PoE for switches that provide PoE, but not external injectors. There are two standards for power, if the power is injected off the switch it uses dedicated pairs, if it is injected on the switch it uses the data pairs (phantom power).
      • And it is a trivial case to inject power into the ethernet stream ... look at a circuit for putting repeater power on a T1 span from the late 70s ... You just need to redo the magnetics to handle the higher passband of Ethernet.

  • As much as the AC standard can be considered a success -- even if different regions use different voltage and connectors, the sorry state of the DC power is an outrage.

    Why does every DC-using device come with its own adapter, and uses its own voltage? Why could not we standardize that?

    Maybe, this "power over Ethernet" initiatives (together with the "power over USB") will spell the end of power-strips with curiously shaped "bricks" constantly falling out of them...

    • It's happening. Slowly. Somewhat. Even over the past few years, I've noticed things slowly gravitating to either 5v or 12v. I think part of this has to do with the 12v lines used by hard drives (eg the mini-itx market is pushing htis), and the 5v is used by a lot of chipsets, apparently (since every decent PDA seems to run off 5v). So we might get there eventually.

      Personally I think it would be great if 12vdc was the "standard" dc power supply, and you can easily get or make an adapter to turn it into
      • Cell phones usually run on 4.8V, because you can only get multiples of 1.2V when you couple rechargeable batteries in series (non-rechargeables carry up to 1.5V, so that's why 3/6V is common in toys and the like).

        In fact, 1.5V (or a multiple thereof) was a pretty good standard until rechargeables came along. That's also why one of them flatty squarry batteries is 9V, a multiple of 1.5..

        The problem of course is that while you can easily go from 1.5V to 3V and up by coupling batteries in series, if you've g
      • Most solar systems run 12V DC, and I noticed all of my networking equipment does this, too. Maybe there's a market for solar powered repeaters?

        Or maybe I could put one in my shed so I can hide there when my mother-in-law comes over.

    • Why does every DC-using device come with its own adapter, and uses its own voltage? Why could not we standardize that?

      Because if you did, you'd still need a bunch of DC-DC converter bricks.

      An external hard disk has different power needs than a 5.1 speaker system which has different power needs than a cordless drill (charger), which also has different power needs than my cellphone. If you demanded that all that stuff have a plug on it for a certain DC voltage, all you're going to see is whole bunch o
      • Most electronics have a DC-DC converter built in these days. MY little linksys wireless router for example runs off a 12vDC wall wort but internally everything is running at 3.3v

        Switching regulators are pretty damn effiecent, some text even refer to them as DC transformers. They are also pretty small, ususally just a small 4 or 5 pin device with a few small inductors, resistors and capacitors.
      • Because if you did, you'd still need a bunch of DC-DC converter bricks.

        I'd need a lot less of them, than I have now. There being a standard of, say, 12V or 24V would give the designers and manufacturers a good incentive to stick to it, unless their specific product requires something different.

        What we have now is gratuitous diversity of the "bricks", which should be interchangible, but are not. Not all manufacturers even have the decency to standardize within their own products.

        What you're asking is l

    • "Maybe this will spell the end of power-strips with curiously shaped "bricks" constantly falling out of them..."

      As to the "falling out" bit, one good solution is British Standard 1363 [] - I never did understand why people put-up with power cables that get disconnected every time you move them too far.

  • Work hazard (Score:4, Funny)

    by Ceriel Nosforit ( 682174 ) on Thursday December 16, 2004 @03:59PM (#11108372)
    There goes the only type of devices I don't repeatedly electrocute myself on. =(
    Damn you! Damn you to heck!
  • by Technonotice_Dom ( 686940 ) on Thursday December 16, 2004 @04:05PM (#11108465)
    I've seen this implemented in a local school (in the UK) that issues all staff with laptops. The laptops then have a student register application running on them, and the staff can wander across the building using it. They've put up lots of D-Link access points scattered all over their buildings, just mounted to the wall on wooden boards - an ethernet cable appears out of the wall, or from a socket, into a little box (size of PCMCIA card, but thicker) which then has two cables (power + ethernet) going into the access point.

    Appears to work very well for them.
  • You can trickle-charge your electric car on only 13W, if you are willing to wait long enough!
  • To install my Network cable because it all has to be properly installed/grounded etc. now that it is carrying electricity?

    The electrical union must LOVE PoE they have been trying to get state electrical code written to include low voltage wiring for years, maybe PoE will be enough to get it changed :/
  • For my brand new Prescott based computer I need at least 390W :)
  • Can't wait until power over wireless connections become available.

    then you'll really have something.
    • Nicola Tesla already invented power over wireless in 1908. His invention was scratched, because having wires mean to control energy distribution and money.

      However, with an array of properly tuned antennas, you can already draw significant amount of power (somtimes in order of watts) from near cell phone towers, radio stations, radars, until you get caught by team equipped with proper field gradient measuring equipment.

      Anyway, using modulated signals as a source of power somewhat reminds me of burning boo
  • What... (Score:3, Funny)

    by fizban ( 58094 ) <> on Thursday December 16, 2004 @04:18PM (#11108583) Homepage the world coming to?

    Power over ethernet! Internet over power lines! Human sacrifice! Dogs and cats, living together! Mass Hysteria, people!
  • by Tezkah ( 771144 ) on Thursday December 16, 2004 @04:18PM (#11108591)
    I'd really like to see an electric razor that had a version of Windows on it. You'd be shaving your face, and then a holographic Clippy would pop up: "It looks like you're shaving your face, would you like tips on shaving your junk?"

    I'm pretty sure that should be the prompt he'd give you no matter what you're shaving. "It looks like you're shaving your head, would you like tips on shaving your junk?"
  • Imagine a Beowulf cluster of electric razors...
  • Electric razors? (Score:5, Insightful)

    by RealAlaskan ( 576404 ) on Thursday December 16, 2004 @04:23PM (#11108634) Homepage Journal
    Bizarre uses include electric razors.

    I'm trying to think of places where I have seen an ethernet jack but no wall power. Hmmm .... zero. Never seen such a place.

    Now I'm trying to think how many times I've wanted to shave in a room which contained an ethernet jack. Hmmmm .... zero.

    So, come on, somebody, tell me why you would buy a power-over-ethernet razor. I'm stumped.

  • Power over USB (Score:2, Informative)

    by elhaf ( 755704 )
    The usb spec already provides a certain amount of power to drive things like small gameboy lights or memory stick readers, but these don't always work. For instance, you sometimes have to get a Powered USB Hub [] just to drive devices such as card scanners. And then you have to plug that in.
  • I would much rather have devices support "ethernet over power" than "power over ethernet". That would cut the cost of rewiring buildings substantially and you wouldn't have to worry about the low power available w/ PoE. Unfortunately, the powerline network products I've seen aren't nearly fast enough.

    For the average person, running ethernet cable into the den for the Tivo-like thing that has a network port is bad news. There's already cabling in the den, and every room of the house, for power, it makes
  • Had an outdoor wireless router power supply melt which caused a major outage. The out of production power supplies were a tad hard to find so we just used the POE adapter and it's been running fine ever since.
  • by adb ( 31105 ) on Thursday December 16, 2004 @04:46PM (#11108924)

    Right now it triples the price of a switch []. (Compare the 2626 and 2626-PWR, for example.)

    So no.

  • It would be sooooo convenient for home theater owners to no longer have to worry about wiring the damn house up for the latest Dolby 19.1 digital surround sound.

    Just plug the speakers into the wall and viola!

    power + audio. :)
  • Possible Uses? (Score:5, Interesting)

    by pete-classic ( 75983 ) <> on Thursday December 16, 2004 @04:51PM (#11108982) Homepage Journal
    Possible uses for Power over Ethernet

    Finally convincing the fucking cat to not chew on the cables?

    • by puzzled ( 12525 ) on Thursday December 16, 2004 @05:14PM (#11109257) Journal
      I lived with this chick that had a cable chewing cat some years ago. One day one of my college roomies stopped by and as we were talking kitty walks out and starts in on the phone line in the living room.

      Mike looked at me, got the *biggest* grin you've ever seen, then whipped out his cell phone and pressed redial ...

      Kitty rang, backed up, hissed, then bit the cable again just in time for the third ring. Now I liked that cat and I have a long hair tortoise shell of my own, but I sure was glad that Mike cured that cat of ripping up cables.

  • this becomes like power over USB is now. heh i can just see reading lamps powered over ethernet.
  • So how long before some one comes up with a mobo that will run off of this?

    In large deployments, this could be very useful.
  • Wake me up when they get it working over Wi-Fi ethernet.
  • Some uses (Score:4, Interesting)

    by owlstead ( 636356 ) on Thursday December 16, 2004 @05:23PM (#11109346)
    Just to fuel your imagination, I've put in some nice uses:
    - Networked camera's (more zooming, tilting and maybe even lighting with 39 W)
    - Networked printers
    - Home server appliances (my VIA EPIA runs great with DVD player and 3.5" HDD on 53W, it would run just great on 39W without the DVD player)
    - Media players (MPEG4 & MPEG 2 layer 3)
    - Downlink switches

    And I do not have a clue why they never use this for PDA's. Use a common network plug to synchronize your PDA, and give the customer a nice powered switch or network adapter instead of those stupid cradles.

    Currently the standard is mostly found in Remote Access Points. I would have put my access point (which is at the best place for RF, but not for cables) on power over ethernet, but these components are hard to find. Just putting 5 V and splitting it at the end does not seem to work, probably because of the distance.

  • by Myself ( 57572 ) on Thursday December 16, 2004 @05:24PM (#11109367) Journal
    ... lots of smaller devices (PDAs, older laptops) draw under 20 watts. The wall-wart for the Vadem Clio (sitting right here) only puts out 11 watts, and that's enough to apply a mild charge to the batteries while running the device.

    Around the time HPNA powerline ethernet came out, I waited eagerly for a laptop maker to announce an AC adapter which would also bridge the machine to the network. No such device ever emerged. I'd love to be able to curl up on the couch with a network-connected device and not worry about the battery. I'd be happy to drop an RJ45 outlet in the corner. Will someone make a device that'll use both signals from the same cable?

    Being low-voltage, you don't need to call an electrician to move network cable around. Thank goodness. There are murmurs within the electrical industry of trying to legislate a change to this, be watchful and let your representatives know that low-voltage wiring is not hazardous and should remain unregulated.

    One problem with PoE is deciding which device gives and which receives. Right now, the cable modem, the router/firewall, and the 8-port switch all have wall warts. With PoE this could be reduced to one, but which one? For a simple star layout, it's simple. I fear the mess of adapters isn't going to get much cleaner, however.

    Cameras and APs are the obvious early beneficiaries of this. Another poster mentioned doorstrikes and cardreaders. How about motion detectors, thermostats, and other environmental sensors?

    If the HVAC system is plugged into the ethernet anyway (Or just running back to the same wiring closet, even if it's on separate hardware) then let's toss the duct dampers and other controls onto the same system. Wire the whole building with one type of wire, run it all back to one place, and have flexibility later.

    And since we're replacing all the building's auxilliary systems with PoE connections, how about overhead music / paging systems? Individually addressible bidirectional speakers would enable all sorts of talk-and-listen applications, as well as point control of which programs go where.

    13 watts is also enough for things like cash register scales, receipt printers, barcode scanners, and the like. A lot of that stuff runs on USB now, which is great. I can see applications where remote scales might take advantage of ethernet's distance capability. Also consider that powering down the USB host takes all the devices with it, but with ethernet-attached devices, the network can still "see" the RFID scanner if the register takes a crap for some reason.

    Things like JetDirect print servers would also benefit from wallwartlessness. Yes, decent printers have a slot they sit in and receive power from, but there seems to be no shortage of standalone ethernet print servers.

    How about postage scales that print "electronic postage" from a company's central account? They're great, they never need recharging, but they still need a network connection /and/ a wall-wart.

    And, dare I say it, credit card terminals? We'll just make the manufacturers promise not to transmit the card stripe data in cleartext. (ATMs use some serious encryption, why can't Lowe's?)
  • by meatspray ( 59961 ) * on Thursday December 16, 2004 @08:35PM (#11111211) Homepage
    But what I want to know is can I run ethernet over power on top of power over ethernet?

Nothing makes a person more productive than the last minute.