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Phone Line Interfacing - FCC Part-68

M

mpm

Jan 1, 1970
0
I'm on a data-collection project, and the terminal will download via
POTS.

My question is: We're using the MultiTech Socket Modem (v.34, because
it's low cost).
In the documentation, they show several ways to interface to the phone
line.

We will have a choke in-line for the tip and ring for common-mode.
And a resettable fuse. So far, so good.

But I have a question:
MultiTech shows a paralleled 220pf 5kV cap & a sidactor (transorb),
with one set each on both the tip and ring. The other side goes to
"FGND". Any idea what this means, as it's not referenced anywhere
else in the document??

I am assuming Earth ground, or at least some ground other than the
power supply ground driving the rest of the circuity. (There is also
an analog ground for the modem speaker - which we're not
implementing...)

Our box will be just that: A plastic box with a membrane keypad, an
LCD, a 9VDC 2-conductor wall-wart power supply, and of course, an
RJ-11 for the phone line. There will not be an earth-grounded
conductor.

Should we bother with the (Y2-rated safety) caps and sidactor
(transorb) protection, or just go with the common mode choke and
inline fuse? What is "safe", if anything, to connect to power
supply ground? Will the choke & fuse only arrangement pass FCC -68
requirements?

Thanks. (Seems like ages since I did any work with embedded dial-up
modems!)
-mpm
 
M

mjkaras

Jan 1, 1970
0
I'm on a data-collection project, and the terminal will download via
POTS.

My question is:  We're using the MultiTech Socket Modem (v.34, because
it's low cost).
In the documentation, they show several ways to interface to the phone
line.

We will have a choke in-line for the tip and ring for common-mode.
And a resettable fuse.  So far, so good.

But I have a question:
MultiTech shows a paralleled 220pf 5kV cap & a sidactor (transorb),
with one set each on both the tip and ring.  The other side goes to
"FGND".  Any idea what this means, as it's not referenced anywhere
else in the document??

I am assuming Earth ground, or at least some ground other than the
power supply ground driving the rest of the circuity.  (There is also
an analog ground for the modem speaker - which we're not
implementing...)

Our box will be just that:  A plastic box with a membrane keypad, an
LCD, a 9VDC 2-conductor wall-wart power supply, and of course, an
RJ-11 for the phone line.  There will not be an earth-grounded
conductor.

Should we bother with the (Y2-rated safety) caps and sidactor
(transorb) protection, or just go with the common mode choke and
inline fuse?    What is "safe", if anything, to connect to power
supply ground?  Will the choke & fuse only arrangement pass FCC -68
requirements?

Thanks.  (Seems like ages since I did any work with embedded dial-up
modems!)
-mpm

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
 
C

CampKohler

Jan 1, 1970
0
I'm on a data-collection project, and the terminal will download via
POTS.

My question is:  We're using the MultiTech Socket Modem (v.34, because
it's low cost).
In the documentation, they show several ways to interface to the phone
line.

We will have a choke in-line for the tip and ring for common-mode.
And a resettable fuse.  So far, so good.

But I have a question:
MultiTech shows a paralleled 220pf 5kV cap & a sidactor (transorb),
with one set each on both the tip and ring.  The other side goes to
"FGND".  Any idea what this means, as it's not referenced anywhere
else in the document??

I am assuming Earth ground, or at least some ground other than the
power supply ground driving the rest of the circuity.  (There is also
an analog ground for the modem speaker - which we're not
implementing...)

Our box will be just that:  A plastic box with a membrane keypad, an
LCD, a 9VDC 2-conductor wall-wart power supply, and of course, an
RJ-11 for the phone line.  There will not be an earth-grounded
conductor.

Should we bother with the (Y2-rated safety) caps and sidactor
(transorb) protection, or just go with the common mode choke and
inline fuse?    What is "safe", if anything, to connect to power
supply ground?  Will the choke & fuse only arrangement pass FCC -68
requirements?

Thanks.  (Seems like ages since I did any work with embedded dial-up
modems!)
-mpm

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.
 
M

mpm

Jan 1, 1970
0
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.- Hide quoted text -

- Show quoted text -

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!!
 
W

w_tom

Jan 1, 1970
0
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 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.
 
J

JosephKK

Jan 1, 1970
0
I'm on a data-collection project, and the terminal will download via
POTS.

My question is: We're using the MultiTech Socket Modem (v.34, because
it's low cost).
In the documentation, they show several ways to interface to the phone
line.

We will have a choke in-line for the tip and ring for common-mode.
And a resettable fuse. So far, so good.

But I have a question:
MultiTech shows a paralleled 220pf 5kV cap & a sidactor (transorb),
with one set each on both the tip and ring. The other side goes to
"FGND". Any idea what this means, as it's not referenced anywhere
else in the document??

I am assuming Earth ground, or at least some ground other than the
power supply ground driving the rest of the circuity. (There is also
an analog ground for the modem speaker - which we're not
implementing...)

Our box will be just that: A plastic box with a membrane keypad, an
LCD, a 9VDC 2-conductor wall-wart power supply, and of course, an
RJ-11 for the phone line. There will not be an earth-grounded
conductor.

Should we bother with the (Y2-rated safety) caps and sidactor
(transorb) protection, or just go with the common mode choke and
inline fuse? What is "safe", if anything, to connect to power
supply ground? Will the choke & fuse only arrangement pass FCC -68
requirements?

Thanks. (Seems like ages since I did any work with embedded dial-up
modems!)
-mpm

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.
 
R

rickman

Jan 1, 1970
0
I'm on a data-collection project, and the terminal will download via
POTS.

My question is: We're using the MultiTech Socket Modem (v.34, because
it's low cost).
In the documentation, they show several ways to interface to the phone
line.

We will have a choke in-line for the tip and ring for common-mode.
And a resettable fuse. So far, so good.

But I have a question:
MultiTech shows a paralleled 220pf 5kV cap & a sidactor (transorb),
with one set each on both the tip and ring. The other side goes to
"FGND". Any idea what this means, as it's not referenced anywhere
else in the document??

I am assuming Earth ground, or at least some ground other than the
power supply ground driving the rest of the circuity. (There is also
an analog ground for the modem speaker - which we're not
implementing...)

Our box will be just that: A plastic box with a membrane keypad, an
LCD, a 9VDC 2-conductor wall-wart power supply, and of course, an
RJ-11 for the phone line. There will not be an earth-grounded
conductor.

Should we bother with the (Y2-rated safety) caps and sidactor
(transorb) protection, or just go with the common mode choke and
inline fuse? What is "safe", if anything, to connect to power
supply ground? Will the choke & fuse only arrangement pass FCC -68
requirements?

Thanks. (Seems like ages since I did any work with embedded dial-up
modems!)
-mpm


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.
 
M

mpm

Jan 1, 1970
0
What do you mean 'old days'?

I also seem to recall a D25 connector and cable connecting said modem to
a gadget called a computer. Pin #1 is "Frame Ground", running from this
common mode point in the surge protection, to the modem 'frame' (if any,
given that most are plastic boxes) through the RS-232 cable to the PC
chassis.

--
Paul Hovnanian     mailto:p[email protected]
------------------------------------------------------------------
One World, One Web, One Program - Microsoft Promotional Ad
Ein Volk, Ein Reich, Ein Fuhrer - Adolf Hitler- Hide quoted text -

- Show quoted text -

You know Paul, that's an astute observation.
Pin-1 was equipment ground on a DB-25, though a lot of manufacturers
didn't use it that way (if at all).
And I can't tell you how many (ground loop) problems I encountered
with cableing that occasionally connected the electrical ground to
circuit common...

This MultiTech modem is a pretty neat device. Basically, an embedded
block - that will sit as a daughter board on the finished product. It
doesn't need RS232 levels, because you can "talk" to it with simple
logic level.

So, as I was already in the "frame" of mind (no pun intended) to
ignore all the modem RS232 stuff, I had forgotten about Pin-1. The
socket modem has a DAA on it, so really, all I need to do is take care
of the common mode rejection, and fuse the line. Well, that and watch
where I put the traces on the PCB.

Thanks.
-mpm
 
W

w_tom

Jan 1, 1970
0
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 protectphoneline 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
thephoneline. It will roll in on the wire and fry every thing
connected, protection or no. But a close by strike will create a
voltage/currentsurgein the line which can be protected against
depending on the strength.

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.
 
W

w_tom

Jan 1, 1970
0
Were do they still use that much areial cable? Around here most telco
plant is underground, and fiber optic.

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.
 
R

rickman

Jan 1, 1970
0
First of all, there is no classic CO around here. There are fiber to
copper to serve small neighborhoods. As usual, you have your head up
your ass, because Verison doesn't provide any service in this area.

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.
Another _wierd_tom_ straw man.


Bullshit. It used to be. They were even even stretched between
wooden things called 'poles', way back in ancient history.

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 deny that Verison or their FIOS is anywhere near my part of
Florida. Not that you know the difference between the various baby
bells.


Absolutely nothing. The so called 'protectors' are routinely blown
off the sides of houses and out of pedestals in Florida. If you knew
even 1% of what you claim to, you would admit the truth. I have seen the
required ground wire melted after a protector was vaporized.

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.

I have only seen overhead cables installed as temporary repairs in
the last 20 years. This area started the conversion to fiber over 25
years ago. As usual, you have your head up your ass.

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.

Dumb ****. Lightning does not travel miles to a nonexistent
traditional Central Office. Get your head out of the '70s and see what
is being used these days. This subdivision is less than a mile from
where everything is converted to fiber. You are so out of date you have
no idea how it works, or that the conversion was done because of
constant repairs to Telco C.O. equipment from lightning damage, along
with vaporized pairs in the underground cable. Most of that was over six
feet deep in the downtown areas. You have no concept of reality, yet you
continue to run your ignorant mouth. The last of the fiber conversion
was done to add DSL capability to outlying areas.

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
 
M

mpm

Jan 1, 1970
0
� 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 requiredas
has been routine in telcos for 100 years to avoid surge damage.


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: http://www.access.gpo.gov/nara/cfr/waisidx_07/47cfr68_07.html

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...
 
W

w_tom

Jan 1, 1970
0
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: http://www.access.gpo.gov/nara/cfr/waisidx_07/47cfr68_07.html

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.
http://www.psihq.com/AllCopper.htm

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:
http://www.copper.org/applications/electrical/pq/casestudy/nebraska.html
First and foremost, the entire electrical system must be properly
installed according to NEC requirements. ...
It is absolutely imperative that all surge suppressors be grounded.

Or learn from another professional what an effective surge protector
does:
http://www.telebyteusa.com/primer/ch6.htm
Conceptually, lightning protection devices are switches to ground.
Once a threatening surge is detected, a lightning protection
device grounds the incoming signal connection point of the
equipment being protected. Thus, redirecting the threatening
surge on a path-of-least resistance (impedance) to ground
where it is absorbed.
Any lightning protection device must be composed of two
"subsystems," a switch which is essentially some type of
switching circuitry and a good ground connection-to allow
dissipation of the surge energy.

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:
http://www.harvardrepeater.org/news/lightning.html
Well I assert, from personal and broadcast experience
spanning 30 years, that you can design a system that will
handle *direct lightning strikes* on a routine basis. It takes
some planning and careful layout, but it's not hard, nor is
it overly expensive. At WXIA-TV, my other job, we take
direct lightning strikes nearly every time there's a
thunderstorm. Our downtime from such strikes is almost
non-existant. The last time we went down from a strike,
it was due to a strike on the power company's lines
knocking *them* out, ...
Since my disasterous strike, I've been campaigning
vigorously to educate amateurs that you *can* avoid
damage from direct strikes. The belief that there's no
protection from direct strike damage is *myth*. ...
The keys to effective lightning protection are surprisingly
simple, and surprisingly less than obvious. Of course
you *must* have a single point ground system that
eliminates all ground loops. And you must present a low
*impedance* path for the energy to go. That's most
generally a low *inductance* path rather than just a low
ohm DC path.

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:
http://www.polyphaser.com/technical_notes.aspx

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:
Lightning surges cannot be stopped, but they can be diverted.
The plans for the data center should be thoroughly reviewed to
identify any paths for surge entry into the data center. Surge
arrestors can be designed into the system to help mitigate the
potential for lightning damage within the data center. These
should divert the power of the surge by providing a path to
ground for the surge energy. ... It is also necessary to protect
against surges through the communications lines. The specific
design of the lightning protection system for the data center will
be dependent on the design of the building and utilities and
existing protection measures.

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:
http://www.cinergy.com/surge/ttip08.htm
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:
The purpose of the ground connection is to take the energy
arriving on the antenna feed line cables and control lines (and
to a lesser extent on the power and telephone lines) and give
it a path back to the earth, our energy sink. The impedance
of the ground connection should be low so the energy prefers
this path and is dispersed harmlessly. To achieve a low
impedance the ground connection needs to be short
(distance), straight, and wide.
...
The goal is to make the ground path leading away from the
SPGP more desirable than any other path.

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:
http://www.arcelect.com/lightnin.htm
As previously mentioned, the connection to earth ground can not
be over emphasized.
...
Conceptually, lightning protection devices are switches to ground.
Once a threatening surge is detected, a lightning protection
device grounds the incoming signal connection point of the
equipment being protected. Thus, redirecting the threatening
surge on a path-of-least resistance (impedance) to ground
where it is absorbed.
Any lightning protection device must be composed of two
"subsystems," a switch which is essentially some type of
switching circuitry and a good ground connection-to allow
dissipation of the surge energy. The switch, of course,
dominates the design and the cost. Yet, the need for a good
ground connection can not be emphasized enough. Computer
equipment has been damaged by lightning, not because of the
absence of a protection device, but because inadequate
attention was paid to grounding the device properly.

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:
http://scott-inc.com/html/ufer.htm
http://members.aol.com/gfretwell/ufer.jpg
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
The primary protector grounding conductor shall be as short
as practicable. ...not to exceed 6.0 meters (20 ft) in length.

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.
 
R

rickman

Jan 1, 1970
0
In some areas they are pulling out the copper and replacing it with
fiber, to keep from having to tear up roads and sidewalks. The cast
concrete conduits are almost full of copper, so they pull one cell full
of fiber and transfer a large block of the traffic to it, then pull out
the old wire and repeat, till everything has been updated. A couple
years ago I visited the Sprint warehouse in Eustis and saw maybe 50
tractor trailer loads of scrap lead and plastic cable they had pulled
from service. They had a company that would come in and use a machine
to remove the outer jacket, and wind the scrap copper wire on big spools
to take it to a refinery. That had over 1000 spools of different fiber
and copper cable in stock, but told me they couldn't wait to get rid of
as much copper as possible. They had purchased Florida telephone a few
years before, and it was like a 1940's telco museum with all the old
junk they kept in service.

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.

Poles don't last that long in Florida. Between high winds, lightning,
drunk drivers, and woodpeckers a lot of poles last 20 years, or less.

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.
The same 'right of way' is needed for overhead lines which is granted
by local, county and state governments. The same goes for electric and
CATV lines. The electric and CATV are still overhead on my street, but
they replaced the aerial cables over 10 years ago. The subdivision was
built in 1964 so it was simpler to trench in the underground cable to
new pedestals, and change one drop at a time than to replace an old lead
and paper covered cable in place. A lot less labor, and it left all the
future work at ground level, which reduces the service time and risk of
someone falling off climbing hooks or a ladder.

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.
Undergund cable is fast and easy in Florida's soil. Then the chances
of damage from high winds or lightning goes way down. The land lines
gave better service after the last couple hurricanes than cell phone
service. Their generators had 48 to 72 hours of fuel, and some areas
were without power for two weeks.

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.
Major upgrades were needed, so it was cheaper to build new plant that
keep patching the old. Some areas had been out of spare pairs for
years. They had to bring lines from other nearby areas to back fill.
Then there was the housing boom, lots of new businesses and for a while,
a lot of people wanted two or more land lines. Also, some areas didn't
have any poles because they were too close to a pond or lake to set a
pole. A shallow plastic conduit would keep the cable dry without
spending tens of thousands of dollars to drive concrete pillars into the
soft soil to hold a metal or concrete pole. There are areas of downtown
Ocala i saw with spare plastic conduit for additional fiber. The city's
electric department installed fiber broadband all though the business
district as an incentive to bering businesses to town. I see it once in
a while when i have to visit Ocala.

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.

Actually, I went with Earthlink via the Road Runner fiber optic
backbone before DSL was available in my area. Now that it is fiber to
less than a mile from the house the line is clean. I get long distance
calls from the NE and northern California and it sounds like it's next
door. 20 years ago you had to yell a lot, because of noise on the old
aerial cables. They took so long to upgrade to fiber that I only know a
couple people with DSL in the subdivision. I have repaired computers for
over 25 yeas, so I end up talking to a lot of neighbors with problems.
:(

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

Rick
 
R

rickman

Jan 1, 1970
0
beleive whatever you want. In some places the conversion is cheaper
than constant repairs, and onlp bean counters can't see this.

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.

Everyone shares on copper. I was getting 53k on copper prior to the
switch to broadband, and the switch to fiber by Sprint. The nearest CO
was about five miles away at the time.

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..

I have yet to see good performance from DSL, compared to cable. Some
is barely 128k, and my cable is a little over 7m most days.

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.
 
D

David Lesher

Jan 1, 1970
0
In some areas they are pulling out the copper and replacing it with
fiber, to keep from having to tear up roads and sidewalks.

Poles don't last that long in Florida. Between high winds, lightning,
drunk drivers, and woodpeckers a lot of poles last 20 years, or less.

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.
<http://www.rayvaughan.com/images/telecom/RT/MVC-904Fb.JPG> 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....
 
D

David Lesher

Jan 1, 1970
0
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....


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




You're dealing with the telephone company. We are not subject to
city, state, or federal legislation. We are omnipotent.

Ernestine the Telephone Operator
 
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