POTS Phone Line Power Capability

People say solar and wind power are not practical because of the large storage requirements because of the days they can be insufficient sources. Lightning power would have months of no power. That is going to take some serious backup storage.

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  Rick C. 

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he systems that carry IP are rather much more prone to interruption by the very sorts of events that require emergency communications. The land line based phone system in comparison is a rock.

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. I'm in an area where everything is vulnerable. AC, Cell, Internet. The only thing that might still work is a land line. If I really need it, I k now where the box is at the end of the lane and can clip onto it. I don't think they support pulse dialing anymore, so I couldn't dial by touching th e leads with a jumper.

The failures with land lines are so infrequent they are hard to remember. It is common knowledge that the phone system has a fantastic up time, 99.99

9% is often cited. Are you suggesting that is not the case? Even if you f ound this to not be true with your one line, you do understand that this is an average number, right? That's why anecdotal evidence is not terribly u seful.

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  Rick C. 

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Or instead of tying up the phone for incoming calls a simple resistor can be used to charge the battery while on hook. Of the three circuits needed for tapping into the three modes, the on hook is the simplest. Why not utilize it?

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  Rick C. 

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You may invent all kinds of rules what you want to discuss about, but do not expect anybody else play with your rules.

After all, this is Usenet, in which users take tangents from current threads all the time. Your attempt to be a net cop is futile.

God, you are ridiculous. No one is trying to be a net cop. You are talking about high voltage isolation without making any points relevant to the conversation.

If you have no point, why are you posting? Is this something you are thinking about and wish to make a public record for some reason?

Nothing you have posted is relevant to the design I am talking about. Do you think it is relevant?

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  Rick C. 

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The CO battery plant is allegedly sized to last X hours.

X is not until the on-site backup generator starts, as that is a minute or so. Rather X is the time to get the backup-backup generator there and plugged in, iffen the on-site one fails. That's say 4-10 hours.

(AT&T Long Lines hardened underground stations had 500~750 KVA of generation, and 60-140 thousand gallons of Diesel on site.)

There seldom is. Post-Katrina the FCC was going to require same, but the cellco's cried crocodile tears and the FCC relented.

In a rural area, the driver gets out, starts his chain saw, and removes such obstructions.

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A host is a host from coast to coast.................wb8foz@nrk.com 
& no one will talk to a host that's close.......................... 
Unless the host (that isn't close).........................pob 1433 
is busy, hung or dead....................................20915-1433

I highly doubt the phone companies look for microamps of current draw on the frame of each loop circuit. They never did before I know that. An alarm would go off if the line went permanent signal after dial tone went away.

By real MPPT, I mean maximum power point tracking. Probably takes more power than it does to measure it at those low currents.

Should ask some of those free energy guys on youtube to work on it.

Right. About as practical as trying to harness microamps from the phone line.

Just find a way to disacharge the clouds slowly.

Strowager stepping relays. A lot less trouble than crossbar switches.

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not explaining how any of this is relevant to the discussion at hand.

I lost all the audio inputs on the modulators at a CATV headend that was wi red by idiots. A lighting strike on the 130' tower and improper grounding o f the racks were the cause. They were tied to the neutral of the three phas e feed. They used unshielded telephone wire between the Sat receivers and t he modulators. The antennas were only grounded at the inputs of the HSP. I used a 19" rack panel to ground all of the antennas from the tower. I drill ed through the concrete floor and drove on ground rod per rack, then all of the racks were slid back to the rods, the bad side lifted with pickaxes an d slid over the rods. Then the rods were welded to the racks, and the racks were welded together at the base. The last step was to remove the ground c onnection to the power lines. That was grounded almost 200 feet from our ma in breaker panel, and useless during a lightning strike, like the one that had hit the tower.

the systems that carry IP are rather much more prone to interruption by th e very sorts of events that require emergency communications. The land lin e based phone system in comparison is a rock.

erns

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er. I'm in an area where everything is vulnerable. AC, Cell, Internet. T he only thing that might still work is a land line. If I really need it, I know where the box is at the end of the lane and can clip onto it. I don' t think they support pulse dialing anymore, so I couldn't dial by touching the leads with a jumper.

It is common knowledge that the phone system has a fantastic up time, 99.

999% is often cited. Are you suggesting that is not the case? Even if you found this to not be true with your one line, you do understand that this is an average number, right? That's why anecdotal evidence is not terribly useful.

The Ocala area has thousands of failed pairs in the downtown and resident ial areas. Century Link is unwilling to replace the 50+ year old undergroun d cables, and insist that people wait until it is all replaced with FIOS. P eople with landlines either put up with erratic service, or let the repair crews try to find another usable pair. The downtown has cheap fiber interne t for business use, so most businesses have switched to VOIP phone service.

A drive in near me has a pair of 1Gb/s fiber drops, to back up their digita l projectors, in case one of the movies on hard drive fails. Unfortunately, the fiber service stops two miles from my house, so I have to put up with poor service from Spectrum.

The average lightning current is 30 kA, so if the grounding resistance in the toner grounding electrode is as low as 1 ohm, the tower base will suffer a 30 kV ground jump relative the surrounding countryside ground potential. If everything at the tower base is self contained i.e. no connections to the external world, no problems.

Things get nasty, if there are other networks, such as mains power, telephone and CATV networks separately grounded in the surrounding countryside potential(s). There might be 30 kV potential differences between network grounds.

If there are heavy ground wires to the other network grounds (especially power system grounds) part of the lightning current will flow into the other grounding electrodes. Assuming the total resistance in th mains ground/neutral wire and mains grounding electrode is 10 ohms, then 27 kA will flow directly into the tower grounding electrode and 3 kA will flow through the ground/neutral wire to the mains grounding electrode at some distance from the tower. This could cause damage in a lot of devices connected to the mains but unrelated to the tower.

Things are further complicated by the grounding wire inductance and the sharp pulse dI/dt.

A few years ago in Finland there was a debate why so many modems were destroyed during thunderstorm in particularly close to a cellular tower.

Cellular companies claimed that the tower is forming a protective "cone" to protect nearby houses from direct lightning strikes.

However high cellular towers were erected on dry hills, so I guess providing low grounding resistance would have been a challenge.

Since the towers are mains powered, part of the lightning current would also flow through the ground/neutral (PEN) wire to the distribution transformer located a few hundred meters away. Houses connected to the same distribution transformer also suffered from the PEN ground bounce and the potential difference with the telephone network potential (grounded further away) was too much for some modems.

Even though I had buried telephone lines out at my country home, I lost modems from lightning. It seems that the lightning hits a tree and the tree roots are near the buried line. that was a surprise to me.

Lightning protection is interesting. There are several things that are generally poorly understood. First of all, the lightning strike current does not simply disappear into the ground. An image charge on the earth's surface follows a charged cloud around. When the strike hits, that's where the current goes. Most current therefore flows along the surface of the earth. If the earth is not very conductive, the current may flow somewhat under the surface, probably ripping up the top layer as it goes. So, to ground an antenna tower, you *don't* want a single ground rod driven deeply vertically into the ground. What you want instead are several superficially buried several meter long conductors in a flat star with the mast at the centre.

Another thing is that lightning is a relatively high frequency event. The path preferred by the discharge current is that of least impedance, not that of least resistance. Bends in conductors add inductance, and the current may choose to arc over to a nearby straighter path, even if that path is more resistive. Damage will result because resistance causes dissipation, heat and fire. Lightning protection conductors should follow the shortest and straightest path possible to the centre of the ground star. Again, the current flows along the surface, not through the cross-section, so flat wide conductors are preferred over round ones of the same cross-section.

I saw a nice example of a lightning-hardened mountain-top radio relay that put all this into practice. The antenna was interesting too: basically it was a dipole sprouting from the side of the mast that also served as a lightning rod. The actual dipole sat at the end of a quarter wave stub that began in a short on the side of the mast. The coax connected across the gap between the parallel rods of the stub near the dipole rods. For lightning currents, all this looks like just one lump of connected metal, but for the VHF RF, the shorted stub is a high impedance, so the RF basically sees just the dipole. The coax was strapped to the side of the mast. There was a coaxial spark gap arrester at the base of the mast, grounding the coax shield to the ground star at that point. The radio equipment sat in a metal box at the base of the mast, powered by solar panels on top of the box. This thing takes hundreds of hits with no ill effect.

On that same mountain top, there was also an interesting microwave relay: Just a pair of big dishes connected by a short piece of coax, entirely passive.

Jeroen Belleman

wired by idiots. A lighting strike on the 130' tower and improper groundin g of the racks were the cause. They were tied to the neutral of the three p hase feed. They used unshielded telephone wire between the Sat receivers an d the modulators. The antennas were only grounded at the inputs of the HSP. I used a 19" rack panel to ground all of the antennas from the tower. I dr illed through the concrete floor and drove on ground rod per rack, then all of the racks were slid back to the rods, the bad side lifted with pickaxes and slid over the rods. Then the rods were welded to the racks, and the ra cks were welded together at the base. The last step was to remove the groun d connection to the power lines. That was grounded almost 200 feet from our main breaker panel, and useless during a lightning strike, like the one th at had hit the tower.

That high current through the steel tower also generates a huge magnetic pulse. Unshielded wire turns that into a voltage spike. The audio was bala nced, so no reference to ground, and the inputs to the modulators were CA32

40 made by RCA. (The entire headend was built by RCA) That tower sat about 20 feet up a hill, but the grounding was well under one ohm, and the soil w as moist. That required three, sixty foot deep concrete pours. That require d a permit from the EPA, as well as the pour for the five meter dish. The t ower was a broadcast type, not a TV type for home use. One of the low band antennas weighed 1400 pounds.

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as wired by idiots. A lighting strike on the 130' tower and improper ground ing of the racks were the cause. They were tied to the neutral of the three phase feed. They used unshielded telephone wire between the Sat receivers and the modulators. The antennas were only grounded at the inputs of the HS P. I used a 19" rack panel to ground all of the antennas from the tower. I drilled through the concrete floor and drove on ground rod per rack, then a ll of the racks were slid back to the rods, the bad side lifted with pickax es and slid over the rods. Then the rods were welded to the racks, and the racks were welded together at the base. The last step was to remove the gro und connection to the power lines. That was grounded almost 200 feet from o ur main breaker panel, and useless during a lightning strike, like the one that had hit the tower.

I had lightning hit a barn at my dad's home in Florida. It was close to his C-band Sat antenna. It took that out. That jumped to the buried phone line . It then took out the SLIC, about a half mile away. Then it made it ten mi les into town, destroying that pair.

White Alice didn't bother with antennas on mountains. They used the defr action caused by the peak to bend the signal downward to the earth stations . It was the first 'Over The Horizon' microwave telephone system, built dur ing WW-II to tie the military bases together. It would have taken decades t o build an underground cable system in the permafrost. It was still in use, 30+ years later when I was stationed at Ft. Greely.

Only if it is on their own property. We had a hurricane blow through here and roads and electric lines were down for over a week. Anyone stupid enough to try to deal with that combination themselves deserves to go to jail.

I also know someone experienced with trees and when clearing one from the roadway the tree rolled, freed a branch and got hit in the head. He will never be the same.

Let the pros do the work. They have the equipment and the *correct* training to deal with it.

I used my chain saw so little it was a PITA to maintain it. I gave it to a friend who uses it to cut wood for heat. I think that's a bit silly myself, but it is what his family has always done.

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clear is that the maximum power drawn from the phone line when off hook req uires an MPPT circuit. But that's not terribly important. I did some simu lations using a circuit that emulated a fixed resistor of about 7 kohms. I t would charge up 1 mF to 5 volts in about two ring times.

f hook operating voltage. So clearly that was a bad design.

e you a phone line via a VOIP box which plugs into your home? That may be. But they can't give you that if you aren't on a fiber. Where my one hous e is they would need to run fiber for some 12 miles or more and they ain't gonna do that. My other house could never use a 56 kbps modem because it's on a pair gain amplifier. Know what that is? When you figure it out you may understand that the phone company doesn't update old equipment if they don't have to.

pedia they don't call it an amplifier. That was the term the phone guy use d at the time. Seems it was installed in the 70s when people were getting second lines and they didn't have the copper for it. I was told it was a d igital mux using three phone lines to provide some dozen or so connections. I would guess that's one pair each for data in each direction and one for clocking and sync or just clocking and the sync was in the data.

this is what we have until something drastic happens like hover boards (no t the ebay kind, the Back to the Future kind).

gh.

and/or ringing circuit to account for the line resistance. Actually, I'm not certain either one is needed. The ultimate current is limited by spec, so the MPPT would have limits on the operating envelope.

ial exercise. The "time" you are talking about is on the order of single d igit milliseconds or faster. As I've pointed out, the issue is the limits imposed by the regulations. I don't know the details, but drawing current in excess of the 10 uA allowed but not enough to register as off hook will likely be flagged as a "fault" resulting in notices from your provider. So MPPT is probably without value for off hook operation. Ringing again has limits on the current you can draw, so I'm willing to bet MPPT would violat e regulations.

"Real" MPPT? What is that??? MPPT is just finding the current draw that g ives maximum power. Are you suggesting someone is measuring imaginary powe r instead of real power?

I've already explained that for off hook, the maximum power point is a valu e that can't be used without mucking the phone state. I'm not talking abou t uA. The off hook state is over 10 mA and well less than 24 volts. Once the voltage drops below around 24 volts you have passed the MPPT. Regardle ss of what the phone company is checking for, it is not allowed to draw tha t sort of current unless you are off hook. You can't stay off hook for l ong unless you are making a call. That is checked and the phone line will go into a state where it ignores your on hook condition for some time.

Why do you have such a problem discussing this without the drama?

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