The Telecom Digest for February 08, 2011
Volume 30 : Issue 35 : "text" Format
Messages in this Issue:
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Date: Mon, 7 Feb 2011 08:57:45 -0800
From: Bruce Bergman <brucebergman.remove-this@and-this-too.gmail.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: System Reliability (was Re: New numbering rules for phones in Australia) [OBFUSCATE] please
Message-ID: <AANLkTikNJhnw2xPjve88GMOsb23eFYN7Q9HqZFHakraC@mail.gmail.com>
On Mon, Feb 7, 2011 at 12:20 AM, <telecom-owner@telecom-digest.org> wrote:
>
> Date: 6 Feb 2011 20:16:54 -0000
> From: John Levine <johnl@iecc.com>
> To: redacted@invalid.telecom-digest.org.
> Subject: Re: New numbering rules for phones in Australia
> Message-ID: <20110206201654.19956.qmail@joyce.lan>
>
> > 2) _everything_ that can be delivered over the existing copper can be
> > delivered via FTTH.
>
> Well, other than service that continues working when the power goes
> out for more than a few hours. But apparently nobody cares about that
> any more.
>
Well, not everyone. I have to start shedding excess lines here and convert
a bunch of stuff to VOIP or Google Voice, but I'm keeping at least one POTS
loop on Copper if I have to raise a ruckus to do so. Several of the 'Fiber
to the Home' initiatives building out want you to sign a form agreeing to
move all of your voice data and video services to the fiber, that line gets
crossed out and modified to keep one Legacy POTS over Copper line.
Yes, it's a pain to maintain, but you'll do it. I have my reasons.
***** Moderator's Note *****
>
> Copper's legacy will take a few years to wear off. There are a number
> of services which will suffer with fiber-only local plant: burglar
> alarms, which used to depend on having DC continuity, are now data
> channels - until the power dies.
Once Upon A Time... There used to be simple dry-pair "McCullough Loop"
alarm service, which worked like a telegraph - they ran multiple loops from
the C.O. to a Bunch Block and put all that alarm company's local subscribers
in series. If a premise alarmed, the local alarm panel opened the loop
rotary-dial style with the account number and the zone code that tripped.
Was used for banks and unattended locations because any tampering would be
immediately noticed - the loop goes open.
Nowadays there are security monitoring backups available but there is a
significant added cost to having one, like a SMS or packet radio based
transmitter like AlarmNet. And if it's based on Cellular SMS and the cell
system goes down from lack of proper backup power, your backup system is
worthless.
> Given that many "CEV" sites have less
> than twelve hours of battery backup, any long-term power outage in an
> area with fiber-only plant will leave the entire area without alarm
> service.
That's a whole 'nother discussion, because IMNSHO all critical cell and
wireline Telecom sites should have 96 hours minimum of local backup power
and stored fuel to run those services that need the "Five Nines" reliability
- Hospitals, doctors offices, or just the heart patient living at home. Too
many public safety related agencies have abandoned independent radio systems
(KISS simple analog with backup power at the repeaters) for their more
"reliable" cellphones and Blackberries and complex trunked radio systems
(Nextel), and that's a dangerous fiction.
The Telco's 'Official Disaster Plan' is to deploy portable generators to
small sites where the power is down, but that plan will fail miserably in a
widespread disaster. It's like spinning plates - not enough portable
generators stocked locally ("We'll truck them in from the depot in the next
state!" Yeah, right... On what roads?) or people available to fuel and
maintain them every ~12 hours - and the roads have to be open and passable
to get the portable generators widely deployed, which won't be the case with
many major highway bridges down and roads impassible after a major
earthquake, fire, flood, hurricane, tornado...
It's bad enough when you have to provide local premises power to run your
telephone subscriber equipment, but when the service fails from lack of
power at a midpoint like a CEV or line concentrator, or an amplifier point
on a Cable TV system knocking out their VOIP offerings, then the whole
system has taken a huge step backwards in service reliability.
--<< Bruce >>--
PS: Bill, human-readable Obfuscate please, GMail won't let me at the
headers. Grumble...
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multipart/alternative
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Date: Mon, 07 Feb 2011 15:22:40 -0600
From: Neal McLain <nmclain@annsgarden.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: New numbering rules for phones in Australia
Message-ID: <4D5062A0.2020608@annsgarden.com>
Lisa or Jeff hancock4@bbs.cpcn.com wrote:
> Obviously fibre has advantages in capacity over copper, but does
> that mean existing copper plant should be abandoned?
> Why is fibre cable cheaper to maintain than existing copper
> cable? I would guess that the big maintenance expense of outdoor
> physical plant would physical protection against weather and
> injury and access for maintenance. Wouldn't physical protection
> costs, such as durable outer shells, be the same for copper as
> fibre?
> If say a car knocks down a pole carrying lines, isn't the biggest
> cost labor of the crew to replace the pole and remount the lines?
Robert Bonomi bonomi@host122.r-bonomi.com wrote:
> H*LL no!! When the pole got knocked down, the lines -broke-. The
> labor cost for splicing umpty-hundred pairs -- probably twice
> (since you probably have to insert a _replacement_ section of
> cable as opposed to just re-connecting the broken ends to each
> other) -- probably swamps the cost of re-setting the pole.
Depends on which cables break, where they break, and where the pole
itself breaks.
Except for drops, every aerial communications cable of any description
(copper telephone, CATV coax, or fiber) is almost always supported by a
strand, a grounded 1/4- or 3/8-inch stranded steel cable placed under
tension. The strand provides mechanical support for the communications
cable and prevents the cable from sagging. The communications cable is
lashed to the strand by lashing wire. Examples:
http://www.annsgarden.com/poles/JP0-Strand.jpg
http://www.annsgarden.com/poles/JP0-Strand3.jpg
Note that the strand is not a single wire; it consists of several
(typically seven) individual wires twisted together.
Open-wire transmission and primary electric power conductors are also
tensioned. Tension is maintained by downguys at end poles and corner poles.
If a car "knocks down a pole", there are two possible failure scenarios:
- SCENARIO: The pole breaks off near ground level -- where the car hits
it, or at ground level -- but the upper part of the pole remains intact,
suspended in midair by tensioned stands and power conductors. In this
case, the pole owner can indeed just "replace the pole and remount the
lines" -- more precisely, its own lines. Other pole occupants replace
their own cables. The power utility always goes first; other pole
occupants must wait until the power utility has repaired its facilities
and "cleared" the area before they can work on their own facilities.
- SCENARIO: The pole is physically displaced to the extent that strands
are broken. In this case, the damage to communications conductors may
be extensive. A strand doesn't break cleanly; it stretches, then
individual wires break one-at-a-time, the broken wires untwist and flail
around, until the last wire finally breaks.
When the strand breaks, the communications conductor itself is subjected
to severe tension. But it doesn't break cleanly either -- in most
cases, it will be so badly damaged that it will be necessary to replace
an entire section of cable, requiring two splices. As Bonomi noted,
making two splices in a multiconductor telco cable is a tedious process
that can take many hours to complete.
CATV coax conductors are easier to splice, but restoration still
requires a lot of time. CATV coax stretches before it breaks, damaging
large sections. It may be necessary to replace as much as several
hundred feet of coax.
Fiber cables can be damaged as well. Fiber cable usually contains a
steel or nylon "strength member" to prevent stretching, but if it's
subjected to sufficient tension (which it surely would be if its
supporting strand breaks) even the strength member will stretch and/or
break. If the strength member breaks, everything else in the cable --
jacket, buffer tubes, filler -- will be stretched and break as well.
Furthermore, the fiber itself won't necessarily break at the same place
that strength member breaks; it will break at its weakest point. If the
fiber is in a loose-buffered tube, the actual break point may be several
poles away.
Further exacerbating all of these problems is possible damage from
falling electric power conductors. If an energized transmission or
primary conductor breaks and falls, it may land on a communications
cable or strand. A 13-Kv energized wire landing on a grounded strand
can have interesting results: sparks, smoke, noise, awful smells,
melting insulation. I'm not sure what it would to do a multiconductor
telco cable, the possibilities are interesting to contemplate....
Bonomi continued:
> Needless to say, you can make a few fibre splices in far
> less time than it takes to splice the equivalent umpty-hundred
> copper pairs.
Well, I'm not sure about that.
Even under the best of conditions, splicing a fiber is a tedious
time-consuming process: the cut ends of the fiber must be cut at precise
angles, cleaned with alcohol, aligned perfectly, then sealed with
transparent cement having the same index-of-refraction as the glass
itself. A source of ultraviolet light is necessary to cure the cement.
Fiber splicing jigs usually include a microscope or video camera to
facilitate the alignment process. This is not something that can be
done from a bucket truck during a snowstorm.
And, of course, two splices will be required if there isn't enough slack
in the fiber cable. Slack is necessary not only to replace the damaged
section of fiber cable, but to provide enough fiber cable that the cut
ends ("tails") can be spliced under controlled conditions, usually
inside a vehicle or a tent. Most companies that own fiber networks
either own a vehicle dedicated to fiber maintenance, or have contracts
with fiber-maintenance companies.
(I'm aware that newer splicing techniques, involving fusing the glass,
are available, although I've never used one. So maybe splicing isn't so
time-consuming now, but I suspect it still has to be done under
controlled conditions.)
In addition to the physical difficulties described above, fiber splices
also introduce signal attenuation. One of fiber's big advantages is low
attenuation, allowing for design budgets of only a few decibels of
overhead. But even the best splice can introduce as much as one decibel
of attenuation. Two splices can eat up most of the overhead -- more
than hundreds of feet of unspliced fiber.
Further complicating all this are public works projects such as road and
bridge construction. These projects often require moving entire
polelines. Power, telco, and CATV cables can be spliced -- with
difficulty to be sure, but the work can be scheduled to minimize service
disruptions and signal attenuation.
But if fiber cables must be spliced, we encounter the same problems
mentioned above. For this reason, fiber networks are usually designed
with excess slack. The slack is introduced in "loopbacks" every
thousand feet or so. In a loopback, the fiber loops back for a hundred
feet or so, then loops forward again. These pairs of loops are clearly
evident on roadside polelines, either as loops hanging below the cable,
or supported by "snowshoes". Example:
http://www.optiloop.com/images/fosunit.jpg
I agree with other posters who assert that fiber has enormous advantages
over copper or coax because of its wider bandwidth and lower
attentuation. But I'm not convinced that splicing time is one of them.
In the case of CATV, splicing good old aluminum-sheathed coax is far
easier than splicing fiber. As for telco networks, Bonomi may be right,
I'll leave that for the rest of you.
Neal McLain
Date: Mon, 07 Feb 2011 19:26:46 -0500
From: Eric Tappert <e.tappert.spamnot@worldnet.att.net>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Phone booths
Message-ID: <m231l6dc49tvotlmoa3vb7hfa6mhta8l3n@4ax.com>
Folks,
Tonight on the Philly news there was a story from Bethlehem, PA about
a police booth installed at an intersection near a local hospital to
allow control of an intersection traffic light. The hospital pays the
OT for the cops to operate the light during high traffic hours to
speed things along.
What caught my eye was the booth. It was a telephone booth, albeit
not the nice walnut variety, but an outdoor aluminum and glass one. I
even saw the corner mounting pad for a payphone, fully equipped with
holes for the mounting screws and wiring.
Now I think it is nice that the city went extra lengths to protect the
police officiers from the inclement weather, but my real question is
where do you get a phone booth these days and how much does it cost??
ET
Date: 7 Feb 2011 14:36:00 -0500
From: kludge@panix.com (Scott Dorsey)
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Video conferencing phone booth
Message-ID: <iiphj0$635$1@panix2.panix.com>
> I just want to sit down and begin seeing and talking to some people
>on the opposite coast, for about an hour, right now, without having
>to fly there, and without having to install and learn still another
>Mac app (especially when networking is involved).
Twenty years ago there were a lot of places where you could do this. Many
business incubators, PBS stations and the like had small conference rooms
equipped with the Tandberg teleconferencing systems. The organization I
work for had one of them at each one of its sites.
Skype and other similar services have killed that. They are so cheap and
so convenient that everybody uses them and the fancy teleconferencing
centers are dead now.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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