Can anyone explain what the Ethernet ports are for on a mains extension socket? Googling this returns plenty of results about power line networking but nothing about an Ethernet port on a standard 8-way extension lead.
ATM: Ethernet
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Can only assume it’s for connecting to a computer, having connected one of those mains extenders to your modem.
I’ve got a powerboard with 2 co-ax sockets, rf in and rf out. Haven’t figured what those are for either. It’s got 2 usb sockets though, which is handy.
Could it be a surge-protected extension lead?
I have a Belkin 8-way extension lead with power surge protection. I.E. protection against surges and spikes that might affect computer or audio equipment. Mine also has some pass-through filtered RJ11 sockets for telephone equipment. I think it was bought in pre-broadband days when telephone modems were how one got one’s internet. Possibly others were made later with RJ45 ethernet pass-through sockets but these would now hamper the use of Powerline networking, I would think.
Surge protection can be useful with HiFi gear to stop “pops” from dodgy fridge thermostats and the like kicking in and spoiling your listening pleasure. I keep an old freezer that I use when I’m defrosting the one that’s in daily use. It used to cause annoying “pops” when I was listening to CDs, the radio etc. until I connected my stereo and related stuff through the filtered extension board. Stopped it completely.
I doubt if filtered ports would be particularly necessary for Ethernet lines as data transmission is self-checking anyway. If a data packet arrives corrupted, it just instantly gets sent again when it fails the automatic checking. At broadband or Ethernet speeds this has no noticeable effect.
RF surge protection might be useful for an external aerial source I suppose. Probably wouldn’t be very effective in the event of a direct lightning strike though.
Surge protection, probably
Is that what they call condoms these days?
I’ve had the Ethernet controller on a motherboard fried by a shamefully poor mains power supply (thanks NPower) and now pass all my internal Ethernet traffic to/from the router through pro quality filters; this may be a consumer version of the same, and if so, it’s well worth using it.
Yeah, we had a router fry during a thunderstorm in the mid 90’s. Back then, even though the replacement was a refurb it cost us about £1000 so I wished we’d had some surge protection.
This is one of my areas of professional expertise.
In essence, surge protection on mains extension leads is a con*
Compliant** Ethernet ports should be transformer-coupled so reject common-mode interference (which surges are).
Don’t bother with it.
(*) they all divert the surge energy to the mains earth wire, which is high-impedance at RF as the long thin earth wire is inductive.
(**) not everybody uses properly surge-rated Ethernet transformers, of course.
I run a training course on this stuff. Discount rates for AWers!
Hi fentonsteve , maybe you can shed some light on my experience as mentioned above. At the time my modem/router was plugged into the obvious – phone line and power, and two PCs were networked to it via Ethernet. I came home and noticed the external security lights shining a very odd sulphurous yellow, instead of the normal halogen blast. Our mains supply at the time was (fingers crossed) extremely poor, up and down like the proverbial – to the extent that I had splurged out on a decent APC UPS for the main PC – so my first thought was that we must be having a very low supply voltage event. The only IT kit permanently attached to the mains was/is the modem/router, and given the weird supply status, I didn’t want to risk switching anything else on, so I waited a while. After a while the security lights started working properly again, and the consumer unit still had not tripped, so eventually I dared to fire up the UPS-connected PC. To cut the story short, it transpired that the on-board Ethernet ports in the main PC were both now kaput (but not in the other PC!?) and the router was toast. A new router and a PCI Ethernet card restored connectivity, but I never could understand exactly how a grumbly mains supply headfit could have had that result – any idea?
That does sound like low mains voltage.
Switch-mode regulated power supplies try to keep their output constant. If the input voltage halves, they draw twice as much current to compensate (this is how “Universal” laptop power supplies automatically switch between 230v in Europe and 110v in the US). Unfortunately current makes things hot and, if not adequately rated, burn out.
Also, there’s every chance that after a prolonged low-voltage brownout, the mains voltage momentarily goes way above 230v as it comes back.
And not all Ethernet transformers are made equal. Some break down well before mains surge voltages, although they should all be rated for 2kv or so many are not.
Thanks for taking the time to respond – it’s good to have had some of the physics explained – it’s been far too long since my O Levels! Sounds like I was lucky nothing else got taken out.
What REALLY pisses me off is that when something like this happens, unless you’ve been fried in your bed or without juice for a ridiculously long period you have no comeback on the power supplier at all; with only relatively minor damage, even when it’s clearly attributable to supply-related faults, they just palm you off onto your domestic insurer, who promptly wheel out the teflon exclusion clauses and the ludicrous excess charges.
Cheers everyone. I didn’t buy the extension socket for the Ethernet ports – the one I bought has built-in USB sockets which is a useful feature – but I just wondered what they were used for.
Sorry, @fentonsteve, if it’s not too much hassle, could you explain why an ethernet cable needs surge protection? If, as I presume, the ethernet cable plugs into the modem/router, why isn’t plugging its mains plug into the extension sufficient protection (assuming it works at all)? Where does the ethernet circuit go after it plugs into the extension lead?
As I said above, Ethernet is inherently surge-protected, so the surge-protected mains extension lead is a triumph of marketing over engineering
The common surge scenarios are
1. Electrostatic discharge (the spark you get after you’ve been wearing nylon socks on a synthetic carpet). Every electronic device needs ESD protection or it would blow up the first time you touched it.
2. Lightning strike to the ground, which makes your Earth connection momentarily bounce
3. Lightning strike to power cables, which makes your 240v got to 24000v or so
4. Lightning strike to telecoms cables, which makes your phone line bounce from 50v to 25000v
5. Mains voltage going unregulated which can make 240v got to 500v
Unlike USB (which is 5m max), Ethernet is designed to cover long distances, for example between buildings which might be on different mains supplies with different earthing arrangements. The Earth potential can vary depending on power used and weather (wet soil conducts better than dry soil).
“0v” in some double-insulated equipment can be 120v and 0v in others. Connect the two together and you could have 120v flowing along the Ethernet cable. That’s why Ethernet connections are isolated.
Er, does that answer the question?
Re ESD: 30 years ago, when large screen images were produced on multiple 35mm slides, the AVL Portable Genesis was used to control the banks of projectors. (It was only portable because it had a handle.) They were very prone to static problems in addition to generally being unreliable. IIRC, some programmers used rubber mats.
The Genesis was a departure in that AVL had previously named their products mainly by watching Loony Tunes cartoons: Coyote, Roadrunner, Chipmunk, Eagle, Raven, Dove. Why they decided to name it after an English prog band and not call it Beaver is lost in the mists of time. I’m boring even myself now.
http://i1122.photobucket.com/albums/l522/davebigpicture/Genesis.jpg
An AVL Genesis (not in a skip, where it belongs)
Yes, thank you. Living as I do in an area of frequent electrical storms, i am now officially terrified.
In the event of a storm, avoid holding onto conductive things of different potential. Your phone line takes a different route to your mains power supply, household Earth, and water/gas pipes. Any one could momentarily go up by a few thousand volts, but it would be unlikely for all to be struck simultaneously.
If you have to hold onto a power lead while you stand, for example, in a metal bath during a storm, be sure to wear thick rubber boots and gloves.
Normally, even in a storm, the fabric of your house acts as a Faraday cage and you don’t notice a thing.
We had a lightning strike here last summer that destroyed the router and connected hub. A surge protector between the two may have saved the latter.
I doubt it. There’s enough energy in a surge to do some proper damage. Those surge protectors dump the excess energy into the house protective Earth, which has too high an impedance to be any use. If the surge protector actually did work, the mains extension cable would probably catch fire first.
You’d need one of those copper earth straps (aka lightning conductors) the like of which you see fitted on church spires.