Is this bollocks?

[Graham.]

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[Tim+]

Of a Facebook group a person with an unspecified broadband issue has been advised to get the house earth checked as <quote> “Believe me, it happens all the time in office premises I used to be a network engineer in another life). Some houses effectively don't have earthing at all.” </quote>.

This has got to be bollocks hasn’t it? In the first place I’ve never met a router with an earth and secondly, surely lack of earthing in a domestic situation must be a rare event?

Tim

[Animal]

Sometimes the main earth connection is to a metal water pipe, since replaced with plastic. But there are still going to be other earths in damn near every situation. Copper pipe in concrete? That's an earth if it's on the earth. Gas pipe? That's earthed. Other random bits of metal can be earthed similarly. It's not impossible for a house to be earth free and RCD free, but if it is the earth wiring still forms an equipotential zone.

[Jeff Gaines]

Broadband will work even if one of the copper legs is open circuit, it seems somehow to find its own earth, the 'phone won't work at all in that situation.

I belong to a Facebook group that discusses American "old" houses and a lot have knob and tube wiring which seems astonishing compared to what's required here:

[Davey]

The Greenfield Museum, at "The Henry Ford" (sic) outside Detroit has several original early US houses that were moved there, such as Edison's laboratory, and had a house that was once owned by a famous American. It might have been the Robert Frost house, but it was a long time ago since I was there. It still had the original knob and tube wiring inside, which still, apparently, worked. I shuddered when I saw it.

for a guide to the village. The rest of the place is equally amazing. My wife managed to sit in one of the six Bugatti Royale cars that were ever made, and there is a certain open-topped Lincoln that carried JFK on a fateful day.

[John Rumm]

as a cause of a broadband issue - probably, although no earth at all might reduce the amount of EMI suppression available for tools etc that use a mains filter cap to shunt noise to earth.

Yup, pretty unlikely in this day and age.

Not that unknown... There may be no supplier earth connection and only a partially functional TT one (often just fortuitous earth via the main bonding conductors)

[Paul]

From a percentages point of view, we're talking about a very small number of period houses.

Nobody wants to live in actual crap like that :-/

"But it's an investment." Yeah, sure.

*******

"Typically, the ring conductor has a direct current (DC) potential of −48V to −52V with respect to the tip conductor when the line is in the on-hook (idle) state.

Floating both conductors, not referencing either one to ground, <===== with twisted pair, the noise signals minimizes the pickup of hum from any nearby alternating current induced, can cancel out at the terminus, (AC) power wires. just like it does on transformer-isolated Ethernet "

The choice of a negative voltage, had something to do with galvanic behavior. It is part of corrosion control. Along with installers using gel-connectors for some point to point wiring jobs.

There are around 20 standards for telephony wiring. The highest DC potential between Tip and Ring is -80V in Brazil. Using a Universal Line Card, you can program the card for any one of the 20 standards, and the equipment can be installed in any country.

ADSL at least, is compatible with telephony wiring. Using a "filter", the passband for POTS could be picked off and fed to a regular POTS phone. The higher frequency bands, provide the frequency bins for data transmission. VDSL2 or so, uses frequencies as high as 35MHz. wiki would have actual detail.

The connection to the phone line wire pair (contact 3 and 4 on the RJ11 for Line #1), enters a DAA. The DAA supports various calamities, such as

1100V falling on TIP or RING. This covers the practice of putting telco wiring on the bottom row of telephone poles, and putting electrical power above them (220 VAC comes next, 11kV at the top of the pole). The DAA may also intercept the Ring Voltage (about 180V peak to peak or so in N.A. at maybe 25Hz). Where the phone line enters the demarc area, protection devices can be fitted (gas tube, carbon block), to divert high voltages (like a lightning hit) to ground. The protection devices do not conduct during normal operation.

# There's no ground.

For your connection to the telephony equipment to work, there's a good chance you need both TIP and RING, especially if driving differential ADSL low amplitude signals down the line. ADSL2 at least, is very sensitive to noise sources, including "noise-on-mains" where the wall adapter feeds the ADSL modem. Thru-noise can knock out ADSL Sync. I had that happen here once, and had to replace the offender equipment, to stop it.

The success conditions, can vary, depending on the era of the setup. First generation ADSL, ran all the way back to the CO. Wire length could be 18000 feet (or outside-the-standard, to 36000 feet giving

1.5Mbit/sec rates). Later architectures, the wire only ran 500 feet to the pedestal at the corner, and the electrical conditions there could be different. The pedestal has AC power and a utility meter next to the equipment. Whereas the CO delivered -48V all the way along the long wire run (mainly for signaling purposes, rather than running toasters).

Paul

[The Natural Philosopher]

Looks like total bollocks to me, and anyway an ADSL routers input is straight to an isolated floating balun.

[NY]

Where I used to work, the server room and lab had a series of benches as spines that stuck out from a backbone (like a multi-legged letter E).

Someone in Site Facilities had decided to put each bench on a different mains phase, which meant there were big signs telling people not to connect data cables (Ethernet, RS-232 etc) between equipment on different benches. It had been fine until that floor of the building was refurbished and the lab was put onto lots of separate phases instead of (as previously) all being on one phase.

[Fredxx]

Facebook is a place where you take everything with a pinch of salt.

The incoming line will be isolated from your house mains. The router will use a double insulated power supply. If you use an Ethernet port this will also be isolated, as will Wi-Fi.

In short it doesn't matter how effective, or ineffective, your earth is.

Most of FB is BS, so no change there.

[AnthonyL]

[charles]

quite some years ago, I was at the TV ehibition in Montreaux. I was showing the newly developed CEEFAX. Our signal source was from a VTR 2 floors below. There was a 10v difference between the earths.

[Bob Eager]

Some time ago, my wife worked in a fairly prestigious grammar school in Kent. She was head of computing.

She set up a sixth form Linux lab in an available room. She found out that the room next door was on a different phase, and someone had added extra power points in *her* room ("for the computers") by back wiring through the common wall. She put up big warning notices and reported it as a health and safety matter.

All it did was mark her card. The Head worked hard at getting rid of her, and he succeeded. In the long run, she did well out of it as she is now a senior lecturer in a university!

[Paul]

The four twisted-pair Ethernet cable, has no ground in it, no shield, and is transformer isolated at both ends. A quick search on Google, indicates a "withstand" of a bit more than 2kV. For that to be true, the creepage and clearance around certain areas must be done properly.

Modern Ethernet is "one of the nicest interfaces" on a modern computer. And is a definite improvement after doubly-terminated coax cable and Vampire Taps in first generation.

It's a wonder any of those sort of website is still around. Doubly terminated coax, with ground only on one end.

Paul

[John Walliker]

The insulation in an ethernet transformer consists of two thicknesses of enamel on the winding wires. The primary and secondary wires are often twisted together before winding into the toroidal cores to get the best frequency response. This means that there is really nothing apart from the insulation on each wire to separate them. This is fine for functional purposes but does not count for safety purposes. John

[John Walliker]

I once measured 50V between earths on opposite sides of a room at a newly built medical facility in Los Angeles. It was causing severe mains hum problems in audio equipment whose wiring straddled the room. John

[John Walliker]

Its good that she got a better job, but why is there so much concern about mixing phases in a single room? Each appliance should be properly insulated so it seems very unlikely that anyone could connect themselves between two phases without first dismantling appliances connected to each phase and then holding on to both. How is this different from using a UPS? This provides an output whose phase is likely to be random relative other nearby devices if its input happens to get switched off. The maximum voltage difference between lives from a UPS and a nearby mains powered device could be 2x240V whereas that between two phases of a 3-phase system is only sqrt(3) x 240V. John

[charles]

As I recall, there should be 2m between outlets on different phases. Of course, using extension leads might create problem.

[Joe]

For a year or so, I worked for a company that made large character generation systems. One of their very minor products was a video hum eliminator. They always took a large crate of them to exhibitions and sold most of them.

[The Natural Philosopher]

Event 10base2 - the second generation small diameter coax - has I think isolation transformers on the input.

Out of interest I found this

Which shows (p 5) how the interface to the coax in 10base2 was done. There are electronics directly attached to the cable, but they are powered by a floating 9V supply, and their inputs and outputs are

*transformer coupled* back to the hosts electronics. The implication being that the coax ground need not be the PC ground and *was not connected to it*.