*TOTALLY* isolating phone from line, electrically?

[Mark]

Go to http://www.polyphaser.com

They specialize in lightening protection products and have them for
telephone and datacom applications.

 

[Ken Taylor]

"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:ArXBb.72158$YE3.2843705@phobos.telenet-ops.be...

"Don Bruder" <dakidd@sonic.net> wrote in message
news:SbHBb.1662$XF6.48163@typhoon.sonic.net...

If no such thing exists, has anyone got a good explanation for why not?

In the end the only really good insulator is distance. If lightening can
arc
from a cloud to the ground it can jump a few inches and bypass any black
box
you can invent. It just takes enough voltage.

Having said that.... perhaps you could build something using fiber optics.
You just need to decide how long a length of fibre you need to seperate
the
two ends of your black box. (and solve the power supply problem others
have
pointed out).

You could use a cell phone, albeit with possibly reduced throughput.

Ken

 

[w_tom]

First, if incoming was a phone line, then what was the
outgoing path? Without both incoming and outgoing paths, then
no damage can happen. Second, how do you explain why a
transient completely ignored that telco provided 'whole house'
protector? Phone line typically has surge protection. AC
electric typically does not.

Did a transient enter on phone line, damage modem, then
stop? Of course not. That would even violate primary school
science lessons. Before damage occurred, first a complete
circuit was conducting. Electricity flowed from cloud to
earth via those modems. Only after the complete circuit
conducts through everything in that circuit, only then did one
part become damaged. Where that damage happened does not
define the incoming path. It only defines what was in that
destructive circuit.

An AC electric transient that passes through modems
typically damaged a modem's DAA section. It is, after all,
where galvanic isolation causes highest energy dissipation.
The DAA section is on phone line side of a modem; and often
damaged by surges incoming on AC electric. This from one who
repairs surge damaged modems (even back in the 1200 baud days)
by first tracing a surge path, and then identifying all failed
components. In fact, this modem was repaired after an AC
mains surge damaged its DAA section.

Damning evidence. I not only defined theoretically why
modems are damaged by incoming transients, but also repair
them at the component level - experience also cited.

Again, until one can say why a telco provided surge
protector did not earth the incoming transient, then one
cannot claim modem was damaged by phone line. You can only
speculate that an AC electric transient found earth ground via
that phone line. Incoming modem destructive transient was
from AC electric; outgoing to earth ground on phone line.

Another's technical analysis to the same conclusion:
http://groups.google.com/groups?selm=3cc28cb4.13201880%40news.dingoblue.net.au
or http://tinyurl.com/yqgv

Review your facts. Some IC pins on that serial port card
make a direct connection to one AC mains wire. Use a
multimeter to confirm it if you don't believe it. A direct
connection that bypasses computer power supply. AC mains,
through serial port card, through modem, to earth ground via
phone line. Again, did the surge enter serial port card from
modem, damage card, then stop? Of course not. Serial port
card was in the same destructive circuit as modem. Follow the
path of that surge from AC mains to earth ground via phone
line. Because there is not 'whole house' protection on your
AC mains, then AC mains is a perfect (and usual) path for
surge damage - the complete electrical circuit. How many more
reasons need I post? Another ten? These are damning facts
base on fundamental principles and decades of personal
experience.

Don Bruder wrote:

Since at least four of the dead modems showed obvious signs that the
strike that wiped them came in through the phone line (traces from the
phone jack vaporized, so-called "protective elements" directly
connected to the phone jack traces, and so on, all cooked), I'm
calling it a more-than-reasonable hunch. The other three... Well,
to the best of my knowing, a wall-wart SHOULD cook off long before
allowing a killer spike to get to through to whatever it happens to
be powering. The warts are good (two of them in use as I type, one
with different connector on the end powering my discman player, the
other topping up a set of Ni-Cds), but the modems are toast. Best I
can say is "make your own assumption". The cooked serial port card
was obviously blasted from the direction of the modem (only device
attached to it) and the computer was a "dunno how, but it's got
burnt traces on the motherboard, so it's toast" concept.

Based on that info, if you can tell me which line the strike came
from, you're doing better than me.

 

[w_tom]

How does computer or telephone get electricity if it only
connects to outside world using a fiber optic? Why recommend
a high tech, expensive solution when effective protection
methods are so effective, so less expensive, and proven in
most every town every year for generations? The basic concept
is called earthing - as Polyphaser application notes make
woefully obvious.

Early ham radio operators would suffer damage from
lightning. They would even disconnect the antenna and place
it inside a mason jar. They still suffered damage.
Disconnecting alone did not stop damage. Distance alone (and
that mason jar) was not sufficient. Then they earthed the
antenna. Suddenly damage stopped happening. Of course. That
is the principal behind well proven protection - without fiber
optics.

Any wire that enters the building must first connect to
central earth ground - as Polyphaser so repeatedly
demonstrates. The important distance is the one to earth
ground. Not farther; closer. Connection to central earth
ground typically must be less than 10 feet. Some wires can be
connected directly to earth ground (cable and satellite
dish). Others must make that central earth ground connection
via a surge protector.

Nothing difficult about this. It's old, well proven
technology. Protection is about earthing. Same principle that
makes Franklin air terminals (lightning rods) so effective. A
surge protector is only as effective as its earth ground.

CWatters wrote:

In the end the only really good insulator is distance. If lightening
can arc from a cloud to the ground it can jump a few inches and
bypass any black box you can invent. It just takes enough voltage.

Having said that.... perhaps you could build something using fiber
optics. You just need to decide how long a length of fibre you need
to seperate the two ends of your black box. (and solve the power
supply problem others have pointed out).

 

[Tomi Holger Engdahl]

Don Bruder <dakidd@sonic.net> writes:

OK folks, here's a little something that just blew through this disaster
area I call my mind. Tossing it out for the idea of determining
practicality:

Lightning kills computers and computer gear. We all know this to be a
pretty well established fact. We also know that, in most (not all, but a
very large percentage) cases, the lightning damage didn't come from the
power lines, which are, in general, pretty well protected, either by
compliance with well-researched/written building codes, requirements for
grounding a specific way, surge suppressors (both on the pole and within
the house) and so on. Indeed, most lightning damage seems to come into
the building by way of the phone line, which is nowhere near as heavily
"regulated and sheilded" by building practices. Phone wire runs the
lightning right into the house, cooking off whatever is attached
directly, and sometimes nearby items. Usual scenario: phone line takes a
hit, modem fries, takes computer's serial ports (or even more of the
motherboard) with it.

It might look that the telephone line get the lightning into house,
but thigns are not as straighforward.
What kills the device connected to the telephone line and the mains
power is the huge voltage difference that happens between mains power
and telephone line. This voltage difference can be cause by either:
1. Lightning hitting the telpehone calbe, telephone central office
where the cable goes or nearby the central office. This causes
the telephone line potential to raise
2. The lighting hits the electrical distirbution network. Your whole
ground potential in your house raises to very many kilovolts
This causes the voltage difference between the telephone wires
that are grounded on the one end at the telephone central
that is still the original ground potential (no raise there)

With that in mind, I've just had something resembling a brainstorm, and
want to bounce it off this merry band of electrical lunatics to see if
it's at all practical.

Since the phone line is (or at least, for the sake of this discussion,
I'm "ASS-U-ME"-ing that it is...) the most frequent route for a
lightning hit to follow and cause damage,

It is the combination of mains connection and telephone connection
that causes the msot disasters.

it seems to me that
electrically isolating the phone line from the house and contents would
be the best route to take.

The telephone modems are already isolated somewhat (1.5 - 4 kV osolation).
This is not enough for ay real lighting protection.
Ýou need a very high isolation to make the isolation work.
There are some special products that convert telephone line to
fiber and back, that could help in some this kind of cases.
Quite expensive special solution.

Usually the good enough protection can be made with proper
whole house protection plan, where there are surge protectors
for mains and telephone line, and both of those are connected
togerher and wored to good ground connection. This kind of
arrangement usually limits the voltage differences to something
the equipment can handle.

As of right now, I'm *REALLY* hazy on the
details, but the seemingly ideal implementation would be a box (black or
otherwise...) which plugs into the demarcation point (the place where
the wire from the pole connects to your house, if you're not up on
phoneco lingo) then everything else in the house that needs/uses a phone
line plugs into that.

Anybody ever heard of/encountered such a beast?

Here is one isolator:
http://www.harksystems.com/tower/oc100.html
It promises up to 75,000 Volts isolation (4 inch air gap).

Here are links to some other products:
http://www.optelator.com/

If one exists, what would you expect/be willing to pay for it, and who
would you look to in order to source it?
If no such thing exists, has anyone got a good explanation for why not?

The existing products on the market I mentioned are from around
370 USD and up.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

 

[Tomi Holger Engdahl]

w_tom <w_tom1@hotmail.com> writes:

How does computer or telephone get electricity if it only
connects to outside world using a fiber optic?

A normal PC definately needs the mains power connection
or it needs to be a laptop running on batteries.

If the device is very low power device (just uses
milliwatts or tens of milliwatts), then it is possible
to feed power to it optically through fiber optic cable.

Ot use it off the solar panels from room lighting.

Why recommend
a high tech, expensive solution when effective protection
methods are so effective, so less expensive, and proven in
most every town every year for generations? The basic concept
is called earthing - as Polyphaser application notes make
woefully obvious.

Proper earthing combined with right surge protectors is
a very good solution for this.

Early ham radio operators would suffer damage from
lightning. They would even disconnect the antenna and place
it inside a mason jar. They still suffered damage.
Disconnecting alone did not stop damage. Distance alone (and
that mason jar) was not sufficient. Then they earthed the
antenna. Suddenly damage stopped happening. Of course. That
is the principal behind well proven protection - without fiber
optics.

Any wire that enters the building must first connect to
central earth ground - as Polyphaser so repeatedly
demonstrates. The important distance is the one to earth
ground. Not farther; closer. Connection to central earth
ground typically must be less than 10 feet. Some wires can be
connected directly to earth ground (cable and satellite
dish). Others must make that central earth ground connection
via a surge protector.

Nothing difficult about this. It's old, well proven
technology. Protection is about earthing. Same principle that
makes Franklin air terminals (lightning rods) so effective. A
surge protector is only as effective as its earth ground.

You are right.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/