Phone Line Interfacing - FCC Part-68

For some reasonable ideas go to a discount electronics store and find some low cost POTS product that has a wall wart type powersupply. Buy it and then rip that open and it will likely answer almost all your questions.

- mkaras

I bet FGRD means equipment frame ground, which typically is connected to the power grounding conductor, i.e. the third prong. They want phone line surges to be shunted to earth. Of course, if you want your equipment floating at God knows what when lightning strikes, well, that's your choice, isn't it? Now telco will provide a protector that is (or should be) referenced to earth, but then they designed it to protect their equipment, not yours. And then there's the matter of what your modem is connected to and how important it is that that doesn't get blown, too. If you can't get at the building power ground, I''d go with a nice groundy cold water pipe.

If you can remember the old days (when we all had dial-up modems), they weren't connected to an earth ground. They had an RJ-11 jack, and a wall-wart power supply. That's it.

And those modems were built by the millions. So, surely, safety has been addressed absent a frame ground.

I suspect the "answer" is to just use the common-mode choke and a resettable fuse. The other stuff would be of benefit if you had a frame ground, but in this case (as in so many others) we do not.

I'm probably just going to call MultiTech tech support today to get their opinion. But you're probably right. FGND likely means frame ground.

Thanks!!

And that is what a properly earthed phone appliance has today. Nothing more than a phone line connection and a power supply. Earth grounding the phone appliance does nothing useful. An incoming phone wire must be earthed where it enters the building - a short connection. And yes, that was also standard even in the 1950s - before wall warts and modems.

If not properly earthed where entering a building, then your filter choke will easily be overwhelmed - made irrelevant.

IME, just but a standard DAA line hybrid, with the certifications, and forget about it. It moved the demarcation point a bit in your favor.

If your equipment does not have an electrical connection to anything else, then you don't need the fancy earth ground and transorbs. The transorbs aren't really safety related, IIRC. There are two things you need to protect phone line equipment from, lightning caused surges (not necessarily a direct strike) and AC mains crosses. The lightning stuff is more of an equipment issue. There is not much of anything that you can do which will protect in the event of a direct strike to the phone line. It will roll in on the wire and fry every thing connected, protection or no. But a close by strike will create a voltage/current surge in the line which can be protected against depending on the strength.

A power mains cross with the phone line is a different matter. This can very easily kill anyone touching the equipment if it is not isolated. This is not just the 110 or 220 power coming into the house, but can be one of the higher voltages common on the poles. I want to say the requirements are for 5kV of isolation. That can only be done with transformers, opto-isolators or choppers/capacitors.

Maybe the requirement is only for 2kV. I seem to recall that on one design I did about 8 years ago, the chip I was using chopped the signal into a square wave at high frequency which was passed through 2 kV caps. On the protected side the signal was recovered. BTW, it was a CP Clare chip and it has ***NO*** power supply rejection. If you had 10 mV of noise on the power rail, you had 10 mV of noise in your signal. And believe it or not, you can hear 10 mV of noise on a phone line.

So a telephone Central Office computer; connected to overhead wires all over town; that surges maybe 100 surges during every thunderstorm. That computer must be replaced after every thunderstorm? Of course not. Due to a properly earth surge protector where wires enter the building, then direct lightning strikes cause no damage.

Telcos install an earthed protector to protect their equipment. Telco's protector on your end may do same for your equipment. But only as effectively as an earth ground that you have provided. Surges that do not enter a building need not cause damage. Common mode choke is easily compromised if a surge has no other path to earth. Common mode choke as secondary protection works if surges are diverted to earth via the 'whole house' protector. Surge needs a path to earth.

Let's see. Verizon only started to install FIOS a few years ago. Most every wire connecting to the CO is copper. And for 100 years, direct lightning strikes to that copper resulted in no damage when a protector was properly earthed where it enter the building. Michael A Terrell does not deny this reality.

FCC Part 68 requires this properly earthed protector at both ends of a phone line. What makes a protector so effective? A protector is only as effective as its earth ground.. No protector stops, blocks, or absorbs the typically destructive surge. A protector that earths before those surges can enter a building means protection inside a modem is not overwhelmed. That was known even 100 years ago.

Two 'top of the front page' articles in Electrical Engineering Times define what provides protection in "Protecting Electrical Devices from Lightning Transients". Not a protector circuit. Protection is only as effective as its earth ground and connection to earth ground. How curious. Even FCC Part 68 requires a shorter connection to earth - contradicting what Michael posts.

mpm - more could be learned. Not yet posted because engineering questions are not being asked.

Makes little difference whether underground or overhead (Michael ignores this reality only to argue). Same protection was required as has been routine in telcos for 100 years to avoid surge damage.

[tit-for-tat snipped]

Stop feeding the googlegroups JERK.

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To the best of my knowledge, they are removing very little, if any, of the old phone lines. The fiber is mostly in new neighborhoods. My house is served by sort of copper to a CO that was put in some 50 or

60 years ago. Somewhere in the last 30 years they were running out of copper pairs out this way and they installed a "pair gain amp" which is a type of multiplexor. As a result, I can't get DSL or even 56K modem connections. I am lucky to get 28 kbps connections... and yes, the lines are on poles for most of the mile to the CO. 20 years ago someone (this city I believe) came up with the bucks to bury all the phone and electric lines in the main part of town. Otherwise, if the wires were on poles 50 years ago, they are *still* on poles here.

I don't know why you think they don't still maintain the poles and lines overhead. It costs real money to bury that stuff and I may be wrong, but I think they have to get right of way to bury the lines. They did here, but that was downtown where they had to tear up the sidewalk to bury them.

I agree with that. The protectors will not protect against direct lightning strikes. That can put thousands of volts on the wire and hundreds of amps and actually melt the wire. Even a nearby strike can induce enough current and voltage in a loop to arc through insulation. I have seen this with my own eyes. No sign of a direct strike, but split insulation and melted wire at each point that was near a ground.

But new installation is not the same as replacing prior installations. Maybe in Florida they have incentive to bury the lines because of frequent storm damage. Here the phone company won't even consider burying lines with their own dime.

I only wish they would replace the CO with smaller, more local equipment that would support some sort of high speed. You are one of the lucky ones.

Rick

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There's just too much bullshit, and not any answers worth replying to. For instance, your claim that Part-68 specifies the grounding. It doesn't. (Or at least I did not see it?) See:

To my reading, that information is contained within the document specified by Rule 47CFR68.7(b) In fact, I didn't see the word "ground" anywhere in the entire set of rules.

Now, back to the questions / assumptions / whatever. Michael only asked where that much arial cable was installed, I did not read that as argumentative?? Anyway, those of us who KNOW, (and that includes Michael as I am aware of his background having spoken to him by telephone) can attest that:

Phones line protectors do not always work. No matter how good the protection is, a direct strike can (and usually does) kill it. The "problem" is most engineers don't truly know what a direct strike is. What a lot of folks think is a direct strike is actually one that is some distance away, even though there may still be a slight fault current flowing in the Earth. Any ground conductor (ground rod, etc..) that is driven into soil that is actively conducting a lightning strike is not truly "ground", and is offering somewhat less than optimal "protection", if indeed any protection at all. If you care to know more: I refer you to any of the excellent texts by Martin Uman. (University of Florida Press)

Whether under/above ground or copper / SLIC-fiber electronics, they all suffer from this type of damage... eventually. Generally, underground is better (geometry), and optics are better (lack of conductivity).

As for Telco technology, most of the US (which is where we're deploying the devices) is rather updated, but this is not universally the case. For example, I know a handful of places that still have 5- digit permissive dialing on an ESS-5 or earlier switch. And mostly copper facilities...

Part 68 requires earthing per the National Electrical Code. NEC says that phone line must be earthed by a wire of less than 20 feet. That is for human safety. For surge protection, we both meet and exceed that earthing requirement. For example, better surge protection means that earthing wire is less than 10 feet AND is the same earth ground used by every incoming wire.

When a phone line protector does not work, the human has foolishly assumed the protector provides that protection. It does not for the same reason that lightning rods are also only as effective as their earth ground.

When protection fails, the study (by engineers, not by techs such as Michael Terrell) starts with identifying a defective earth ground. Again, what does Electrical Engineering Times discuss in an articles entitled "Protecting Electrical Devices from Lightning Transients"? Earth ground and connections to earth ground. Where popular myth is common, somehow the protector will stop what three miles of sky could not. Obviously not. Surge protection is about dissipating surge energy where it causes no harm. Protector simply connects surge energy into earth. Protectors that are too far from earth also permits surges to find earth ground, destructively, via household appliances.

You have stated that some "protectors do not always work." Of course. The protectors are only connecting devices. Protection is determines by the connection to and quality of earth ground.

The direct strike is when lightning strikes wires entering your building. Effective surge protection earths that direct strike without damage to the protector. Every phone wire entering the CO from so many subscribers Is (was) copper. Why do telco switching centers suffer typically 100 surges during every thunderstorm without any damage. That CO has the same protector installed at your building

- and an even better earth ground.

Let's see what professionals do to eliminate surge damage. For example, Orange County FL emergency response facilities suffered damage from lightning. Any damage is unacceptable. So Orange County fixed the only reason for their surge damage: earth ground.

In Nebraska, a radio station suffered damage from lightning. Finally, they decided to stop listening to myths; consulted a professional. Well, the professional restored earth ground disconnected by technicians who had listened to myths. And professionals upgraded the earthing:

Or learn from another professional what an effective surge protector does:

Same principles of surge protection apply to radio stations, incoming AC electric, or telephone. Surges are earthed before entering a building or will find destructive paths inside that building. From another professional:

A benchmark for surge protection is Polyphaser. Polyphaser makes a protector that has no connection to earth ground. Why? Because increased distance to earth means less protection. That Polyphaser protector mounts ON earth ground - zero feet away. But again, Polyphaser application notes are considered legendary by those who learned the science rather than the many myths that were posted here by others. What does Polyphaser discuss? Earth ground:

Anyone who knows or demands surge protection discuss earth ground. Sun Microsystems Planning Guide for the Server Room (contrary to the myths posted by others) also says what provides surge protection: Section 6.4.7 Lightning Protection:

Surge protection is determined at the building level by earth ground and having all utilities enter at a common service entrance. If the building was constructed erroneously, a utility explains how to compensate for that defect:

That app note shows wrong, right, and preferred earthing because earthing provided the protector. But then QST Magazine (the ARRL) says the same thing in July 2002:

How curious. That short (low impedance) connection to the single point earthing electrode (SPGP) is also what both 'top of the front page' Electrical Engineering Times articles said. However this remains contrary to many technicians with a history of knowing only what they were first told.

Even the US Air Force says the effective protector must be connected short to earth and where utility wires enter the building. As does lightningsafety.com. As do multiple standards from the IEEE. As does Dr Kenneth Schneider in:

Decide based upon the science or because you like someone. These are mutually exclusive conclusions. The person you like has repeatedly posted in technical error - in direct contradiction to the science from even 100 years ago.

Yes, an earth ground rod is not optimal protection. But the single point earth ground rod is massive protection. Then we spend massively more money to only achieve a little more protection in telephone Central Offices. If earth is conductive, one earth ground rod is sufficient. But if in FL sand and if no surge damage is ever acceptable, then we spend massively more for that little better protection:

Demonstrated is Ufer grounds; originally created to that direct lightning strikes to munitions dump cause no explosion. Just more examples of how direct lightning strikes must not cause damage. In every case, that protection is always about a better conductive path to earth. No earth ground means no effective protection.

The original question is about surge protection for a POTS modem. A common mode choke is only supplementary protection. It will be all but useless if the shunt mode protector connected to earth ground does not exist. Once that 'whole house' protector is properly earthed, only then might the common mode choke provide additional protection. Without a better path to earth before entering a building, that common mode choke will only provide same protection that already exists inside a modem - easily overwhelmed by the typically destructive surge. A professionals always demonstrate, surge protection started by upgrading earth ground to meet and to exceed post 1990 National Electrical Code requirements.

FCC Part 68.215d(4) requires earthing meet NEC Article 800. That is the FCC requiring a short connection to earth ground. Article

800.40.A.4

As every engineering citation notes, every foot shorter than 20 feet (and no sharp bends, separated from other wires, etc) means even better protection. The protector is only as effective as its earth ground - what provides protection.

It may be that copper is being replaced in some situations. But I expect that was trunk lines of some sort and not the wiring direct to homes. Also, you are describing installations that are already underground. Like I said, there are few poles being taken down to install fiber.

Is this a fact? I understand that 87.4% of all statistics are made up. I know for a fact that woodpeckers don't attack phone poles. Woodpeckers bore holes to get insects. There are no insects in poles unless they are already rotten and need to be taken down.

In urban areas, it is *not* the same right of way. A phone company may have right of way for the poles, but that does not give them the right to dig up and bury lines. But the real issue is money. It is very expensive to take out equipment and bury it.

It's not an issue of soil. In an urban area they have to dig up streets and sidewalk. That is not cheap. It may work better, but they don't rip out stuff that works. But I don't live in FL. Maybe it really is worth doing on their own. If so, great. But the rest of the country still has *lots* of phone lines.

I am in an area where there are few if any spare lines. That is why I only get 28kbps on my modem. I am not on a copper pair. I share copper pairs with a bunch of others through an antique multiplexor. I only wish they would replace that piece of crap so I could get high speed.

At least you have it. DSL is only something I hear about... a lot!

Rick

Please don't be insulting. It is not a matter of belief. It is a matter of fact. You can do an incredible amount of repairs to equipment before it becomes cheaper than wholesale replacement and burying. I think I already said that they did that here in a part of town, not because it would save any money, because the city paid for it in order to improve the looks of the downtown. The phone and power companies would have *never* done it on their own because of the enormous cost of tearing up sidewalk and burying lines. Why do you think they strung the lines in the first place, because it is so cheap to do it that way.

I have no idea why you say,"everyone shares on copper". If you are on copper, you typically have a connection directly to the switching office. That is why they call it "copper". Anything else requires conversions from A to D and back to A. In my case the A-D-A is done between me and the CO. Then it is digitized again in the ISPs modem, but the levels have already been quantized and they don't line up with the modem's levels. So they can't use the V.90 technology and the rate is much lower..

We really aren't communicating. I don't care how slow DSL is compared to cable. It is absurdly faster than dialup and lame dialup at that! Around here DSL is 512 and higher for most folks. Of course that varies with your distance from the CO. But at some distance they just won't give you DSL because of the speed problems.

Sorry, but the facts are that you are way out of date on the technology. You are stuck in the '60s, or even earlier.

Not when usable equipment can be salvaged and used for repairs at other sites that aren't growing, or growing as fast. I can see that you don't see the big picture. Do you have any idea what it costs to run a fleet of service trucks? Or how many more you need, if you have to support multiple obsolete technologies? The extra labor costs, because your repair efforts are ineffective?

Florida Power found that out the hard way after the last round of hurricanes hit Central Florida. At least a dozen different types of fusing and switching equipment were still in use, so the people brought in from other parts of the state, and outside contractors spent more time finding the right parts, than doing repairs. The 60 A 7200 line feeding my street was repaired, then it took another 24+ hours to locate a fuse for it, because almost all of that style had been used. Different sections used different equipment and under normal circumstances, trucks & crews were assigned to service an area that had only one or two types of equipment. Not only did it cost a lot more to restore everyone's power, but people who had no power for two weeks or more didn't say, "Well, since you are such nice guys, we'll pay for a normal month even though we barely had electric for a week." If the equipment was standardized, they would have to warehouse less spare parts, have fewer trucks on the road, less line crews and make the dispatch office a lot more efficient.

Have you ever run a component level repair department for a major communications corporation, with physical plants in a dozen states and almost 100 cities? Sometimes a system gets all new equipment just so the old equipment can be tested and shipped to other plants for spares. I did that with commercial grade C-band microwave equipment, so the oddball equipment could be replaced with the same brand and model as all the others at those sites. All defective equipment was sent to my office where I either repaired it, or parted it out to keep other equipment working. Some of the local managers didn't like it, but it saved us a couple million dollars in four years.

For instance: Rockwell/Collins wanted $1500 for the stud mounted bipolar microwave transistor used in the 4 GHz LO, and told us that we had to buy them ten at a time. then wait up to 14 months for enough orders to accumulate before they tested and shipped a batch. They wanted everything shipped to their repair depot, and required you to rent a loaner for $150 a month, and the average turn around on repairs was a little over six months. I started repairing them in house, some in under 15 minutes from the time they failed. they hadn't even cooled off before the bad parts were replaced, the flux cleaned from the PC boards, and they were stuck on the spares shelf in the head end.

I could buy brand new Microdyne 1100 LPR receivers which were drop in replacements for $1200. They had a better noise figure, used less AC, and generated about 10% of the waste heat. Seven of thirteen of the Rockwell/Collins receivers were shipped to me with the promise that if we couldn't fix the five they needed within two weeks they could have any new equipment on the market. I got them that Friday, and shipped six back on the following Monday. I scrapped, and used the others to repair over 20 other units that failed. Average cost to repair was under $50 each. In four years over 10,000 pieces of CATV, industrial computer (Character generators & terminals) and test equipment went through my shop, where under 1% was scrapped, but a lot was transferred from one system to another as upgrades were done.

Did you ever see early overhead phone lines? Have you ever heard of "Phantom Circuits"?

This is what was used before they were scrapped for the lead covered cables. This is another time they scrapped something that worked, for newer and cheaper technology.

The lines were overhead because the early lead & paper covered trunk lines were not suitable for underground installs. Even overhead, they caused problems. A pinhole would let water in and cause crosstalk between pairs, or even worse, migrate through the early plastic and cause electrolysis. that is why you see the large bottles of dry nitrogen used to pressurize lines and keep any moisture out of any possible leak.

Add the fact that not every house on the block had a phone, and they went with the cheapest possible technology. In some places, only one or two houses on the block had a telephone. That thinking included a terminal block that was inside a splice housing on the overhead cable. When I was a kid, there was one or two per block, and that old hard rubber covered steel drop wire could run to the other end of the block before being dropped between 'P' hooks. It doesn't make sense to keep patching aging and failing plant, no matter what business you are in. Otherwise no one would replace old delivery trucks, they would still use mechanical cash registers, and you would still have to use a rotary dial to call the operator to place a call. Why do you think they created direct dialing? The equipment work, and the switchboards didn't need much maintenance. They scrapped that system to go to the stepper or crossbar central office so they could eliminate most of the operators. The same thing happened with the ESS Electronic Central Office. It was smaller, had some diagnostics built in, and didn't require the same skills that repairing or cleaning contacts in a mechanical C.O. The mechanical exchange in Middletown Ohio was built out of parts designed

60 years earlier, and there were no new spares. It was pieced and patched together with salvage from old C.O.s that were being torn down. They said it would be another ten years before they replaced that crap with ESS. Then their biggest customer told them they had exactly one year to fix everything, or they were going private with their 10,000 numbers. here is a picture, before they grew to require that many phone numbers:

A lot of small phone companies refused to do anything, till they reached the point they couldn't afford to do anything and ended up selling out to a bigger company, rather that spend time fighting the PUCO over customer complaints.

All the copper lines here had up to 16 phone numbers per pair.

That was the old 'DC pair' concept and was no longer available in some areas 30 years ago. A line card multiplexes the customers. and another card at the CO breaks it back into an equal number of subscriber lines. Call your phone company and tell them you 'DEMAND" a DC pair and prepare to be cursed at, or laughed at for being a fool. I used to have two way radio customers, with remote heads on leased lines, and a local fire department that used a leased line to control a siren at a paper mill a mile away. All of them had to be converted to RF links or tone signaling equipment when Ohio Bell eliminated all DC pairs. The fire department was easy. The county already had a 'Plectron' selective tone control system to be able to set off any fire or civil defense siren, as needed. We simply put an antenna at the paper mill and moved that receiver to the paper mill. The radio systems could still get a dedicated connection, but it was not a DC pair. We had to use Motorola tone squelch reed relays on some systems, and others required major modifications. Even the city police and county sheriff's radio systems had to be converted, there were no exceptions to the new technology.

The process started right after Ohio Bell finished their conversion from a mechanical to an ESS C.O. They ripped up all the sidewalks in downtown Middletown and burred concrete conduits, then started replacing all the overhead lead cable.

That is why they call it "copper". Anything else requires

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You appear to have a collection of micro-views of telephone plant, some of which are correct. But you really should hold off on generalizing from them.

Copper is alive and well all over the country.

And lead sheathed cable, with paper insulated pairs, was often laid underground.

They are trying to eliminate everything but the last mile of copper around here. I also heard that the state of Tennessee was ready to sign an agreement with AT&T to let them build FIOS anywhere they wanted, without needing local approval.

Not in high acid soil or in places with a high water table. Or so much rock that poles had to be set with a couple blasting caps, per hole. Areas like parts of Cincinnati where a lot of power & telco poles were tagged as "Replace in place". I worked CATV in those areas, and had to put up with idiots demanding the cable drop be buried, even though CG&E, and Cincinnati Bell both refused to bury anything because of the risk of damage from the blasting too close to the homes. Some areas had huge rocks less than a foot from the surface.

As far as generalization, I was trying to point out that there are places that don't conform to the pre '70s style of external plant.

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Interestingly, I just looked on a walk and found many 1964 poles in this DC region....

You guys are mixing apples and coconuts...and ignoring the important ISO layer [below..]

A) The Old Bitch really is Her bastard children. They don't always do the same thing. (But as they get reassimilated into the New Bitch....)

B) When short of copper last mile, or serving some new tickytackytown; the Kids often installed SLC's. SLC's save copper. Copper co$t$.

SLC is really a WECO oops Lucent oops Alcatel trademark, but like "Kleenex..." it gets misused. It's a mux; it takes low-to-mid hundreds of local copper loops and puts 'em on a multiple DS-1's at first, but now onto fiber.

Some Kids [BellSouth] routinely put DSLAMs into their SLC's so you could get ADSL. Others refused to.

C) Occasionally, a Kid used a Pair-Gain [TM]; a 2 {lines} for the price of one {pair} solution. It usually ran ISDN internally, but you never knew it. The gray NIT on your house was changed and you magically got

2 lines. But they are rare vice SLC's.

D) As for protectors, for years She didn't care a whole lot. The protector was designed to protect against lawsuits from customers getting zapped [AND loud bangs in their ear...]; the 300 series phone didn't have anything to get blown up, and 500 series had just varisters. PLUS, they sat on insulated feet on your table.

Later, 2500's and 1A2 came around & She started getting more serious about protectors. Three-element gas tubes are often found; they do a good job but tend to die while on guard duty.

E) Lastly; Verizontal has been hyping FIOS; fiber to the home. If you succumb, they WILL cut down your copper feed [and lie in House testimony about doing so] forcing your "POTS" to require power you supply.

That's because of the most important ISO layer: political. The Kids MUST share existing copper with competitors [COVAD, Speakeasy] but does NOT have to rent transit on the glass; so by forcing you off copper and cutting it down, they sabotage any competition....

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Hmmm... i am confused...are there laws against killing competition? Taft-Hartley etc?