Over here when a cable is 30 years old we might accept having only 80% of the pairs usable.
And you know what? Given the cost of copper, I don't think it is any different over there. Whoever is telling you these things is either not speaking clearly, is pulling your leg, or isn't too bright.
You friend is neither a technician nor an engineer. He sounds like a lineman or an installer. Which is to say that he clearly doesn't understand either how it works, or what the test equipment he uses is actually doing.
Trust me, they measure signal to noise... in *some* way. But installers generally have a little idiot proof box that gets plugged in and does all the tests automatically, and then turns on a red, a yellow, or a green light. He has no idea what it did.
Keep in mind that the original Bell System here in the US was reputed to have been "Designed by geniuses, to be operated by idiots". Particularly in the outside plant area that has not changed at all...
I've always joked that because the Bell System hired all the genius engineers, here in Alaska the telephone system was instead designed by idiots, and required geniuses to operate it! And in fact, due to the remote locations and distances involved, that actually was true to a great degree. :-)
In most places in the US your POTS line becomes one channel of a digital T1 pretty close to your house. A tip is whether a 56kbs modem works for you. That is exploiting the 64kbs T1 channel hardware. The "last mile" is usually the only part of POTS that is analog. There may still be a number five office somewhere in the US, switching analog lines but I am not suure where it would be. Everyone is digital at the central office.
Oh, so the US is technically challenged? Seems unlikely - although maybe in Alaska...................
Are you insane? Ppower line influence is by and large non-existent for digital services. That's the whole *point* of digital - it's *rugged*.
That just shows that you're an asshole (hey, whoulda thunk?). The grunts on the ground doing the actual work are *always* at the cutting edge of technology - they install it!
Actually, you are the one who has so far failed to demonstrate any actual knowledge of current systems.
Tell all you like, the reality is that you *are* guessing - wrongly.
Why am I getting the impression that Alaska really is like Northern Exposure? Are there any normal people up there? Could you put them on the line, please?
You haven't described anything different than what I mentioned.
AND make no mistake... "pretty close to your house" is up to 3
*miles* of cable that is an *analog* tail.
The fact that digital switching has finally become nearly ubiquitous is not significant to the fact that POTS is still delivered as an analog line. (And I might note that here in Alaska we were nearly 100% digitial in the CO more than 15 years ago, at a time when the rest of the US was only 33% digital.)
I don't believe that you know what you are talking about.
In Alaska we have been *far* ahead of the curve in converting from analog to digital. By the end of the 1980's, when the rest of the US was about 33% digital at the CO, Alaska was virtually
100% digital. (The last few holdouts were military bases...)
As has been mentioned previously, it is possible to have as much as 40-50 VAC on a telephone loop. That is not insignificant for digital services. It might be handled well by a regular old (passive) telephone set, but that sort of common mode offset is difficult for digital (active) receivers.
They are usually very well versed about how to use the tools of the trade. Very few of them understand the technology they install. If they did, they would have a different work assignment.
So go find yourself an example of braided shielding ever being used on telephone cable! I've never seen one.
Prior to foil it was common to use a lead sheath for comm cable.
Northern Exposure is fantasy, and so are your concepts.
That's not being picky. It's a vital factor. The service available to a user is limited to what will go down an analogue connection. No matter if that connection is only a few inches long, it's still a bottleneck.
But to continue being picky, the pairs in a length of CAT5 don't know or care if the signal they carry is being called analog or digital, its still just a voltage that varies with time. And the "analog" cable from the phone co distribution box here carries analog voice, and used to carry digital ISDN, and now carries both analog voice and digital ADSL at the same time. So what is it, analog or digital, or maybe it doesn't matter.
BT the main operator in the UK has its exchanges linked together these days by Fibre and has done so for many years now. They break the fibre down to copper at the exchange, add in loop volts and line break etc for older phones, and then route that to the subs premises. However the distances aren't that great, around 3 to 4 miles or so in rural areas and less in urban ones. Using a multipair but what also might make some difference between UK and US practice is that this will invariably be underground plant in their own ducts. An overhead multipair cable is quite rare, and is likely to be of a lowish number of pairs and not that long probably only from a distribution pole to a group of subs not that far away, i.e. a few hundred meters.
The Cable co's in the UK, firms like Comcast and Bellcable etc are now all rolled up into the ntl and Telewest outfit, soon to be renamed again!. They use a similar practice but the distance issue is changed again. They will have roadside cabinets instead of exchange office type buildings, (though they will have a central switch building) that breaks the fibre down using Nokia equipment's to copper to the subs premises. However once again these all are underground ducted cables but the distances there are more likely to be of a few hundreds of yards!.
We don't have this sort of arrangement over here;!...
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In fact I've never seen a phone cable tacked to a power pole carrying more than 240 volts!. And for that the cables are spece'd differently. To have phone and comms cables with power lines at the sort of voltages described on those poles just isn't done here!. The health and safety police just don't allow!! apart from that there is an aversion to overhead plant in the UK most all telecom power services is underground.....
Yes as above. However the market for bizz and residential telephony services is rapidly changing in the UK . Mobile use is now very high and climbing. In fact a lot of young people won't have a landline phone. They see it that a mobile is a "must have" and for around 30 or so pounds a month you can get around 500 minutes a month inclusive calls. Very cheap rates are applied at evenings and weekends.
The extra monthly cost of a phone line can buy quite a bit more call capacity, and the mobility issue a cheap and easy to use text service landlines are finding it hard to compete!.
BT 's 21st century programme is to do away with their circuit switched networks and make it all IP based packet switched. A lot of people use such services as Skype and other phone over the net services. The only thing some people have a phone line in for is for broadband provision!.. However these can and are supplied over radio based nets as well as via UMTS services.
Well it might be over there with all that overhead distribution but it 'taint here!. ADSL is very robust and I've never known a problem with it. And as they use fibre a lot for phone lines between exchanges, not a problem..
Not quite so. One of these guys was quite old and very experienced, and could recall the days of lead covered cable where they had to do wiped joints etc. So don't despise the benefit of experience. Those guys have probably seem more cable close up than you'll ever likely too!.
Course they don't specify it, but some old BT "Poles and holes" staff do know a lot more that you'd give 'em credit for!..
If that makes you feel better, and in someway superior, so be it.. you're welcome;)
Well it seems it isn't always the case here.
As above their use of multipair isn't that great. Its underground and all in cable only ducts. They don't even run mains in there they source that off street lightning cabs..
Once again if its circulating currents in a cable screen as per the original discussion, then for a given diameter of cable there will be a difference between the current that can flow in that a braided multicore will carry more current than one with a ally wrap and small drain wire..
Nope. I don't work for a phone company like you do, but I do have to have a very good working know how of telecoms, phone, appl, private circuit, voice band and wider-band, and ISDN and data..
Nope. Sorry but the "phone engineer" as we know is a vanishing breed:!.
Give you an example. We installed a PABX system for a radio station recently. Its all based on a PC and uses SIP phones. Most all the outgoing calls are over a GSM gateway to other mobiles 70% of calls, and inter office calls are via ADSL. Probably 15 % are carried over the ISDN circuits connecting it to BT. It is now no longer a phone provider service contract issue its an IT one now!..
Actually read that through again;) It isn't that wonderfully written for what they want to convey. I've mailed that off to a few other people to see what they "visualise" that cable to be doing in that description!..
Yes I design and install aerials thanks.
Antenna's are what insects have;)
Yummie. Biccy's is what we call 'em here, dunk 'em in your tea traditionally best stirred with a screwdriver:))
OK on that then..
I've been in TV transmission, Radio broadcasting, studio design and maintenance, data comms, and two way radio......among others...
Errmm... No he's not an engineer. They don't have "them" anymore;-(. You may not know it but most UK industry is run by accountants these days. Once the mighty BBC had an engineering director.. they don't nowadays. They have bullshit speak mongers. Engineers are shat on from a great height, and are treated like dirt, thats why a lot went over there, brain drain we called it;(.
No self respecting UK parent who wanted their son or daughter to do well would have them do engineering. Law, Accountancy, medicine or the civil service are all the "Professions". Engineers?, no way!..
No the one I'm referring to is a technician who does know their system inside out, and is very good at what he does but he won't be there next round of redundancies and job cuts, as the management don't think they need him!.
You haven't seen what some of the subbies get up to. Suppose over there you have your own in house people.
Yes indeed! That is *not* end to end digital service, but describes *exactly* what I've mentioned is done in the US.
The fact that it is the same in the UK merely says that economics is primarily what drives that model.
That is not greatly different than typical US distribution systems. Some places have more buried cable than others, some less.
And there we do have something that is distinctly different, assuming again that you are accurately describing it. Cables here are as shown in the above URL, and that would include poles with high voltage distribution lines at the top. On the other hand, if there is a choice the comm cables will be on poles without the high voltage lines, and they are less commonly put on poles that are for transmission between power stations, though that is done sometimes too, particularly with fiber (which is commonly owned by the power company rather than by a telco leasing pole space).
That is relatively common in the US, though it varies from place to place. Here in Barrow, for example, that style is ubiquitous; but we are sitting on permafrost and the cost of trenching is astounding.
The only buried cables here that I can think of off hand are between town and the area about 2 miles south of town where all the communications satellite dishes are located. Both the power and the communications cables (copper and fiber) are buried; separately of course. What makes that unique here is the lack of an junction boxes for the entire portion (about 1.5 miles) that is buried. There is no other cable run that goes as far without a junction.
Regardless, there are places in the US where cities have banned aerial cables, and everything is underground.
Same here; and my understanding is that we are *way* behind some of the Asian countries in that respect. It is clearly the direction the business will continue to go in the near future.
In Alaska the problem is population density, which isn't high enough to make that economical. That is also true for much of the western US.
I'm sure that it is perhaps worse here, but yes it is important there too.
The reason it is "more" of a problem for digital is a matter of how much drama is associated with the effects. With an analog circuit there is a smooth linear and continuous scale of interference (which also happens to be reduced by the fact that the "receiver" of significance is our ears, which don't hear tones below 100 Hz well). With a digital circuit it is none of that, and while it can operate normally, which is to say error free, at a much lower SNR, the transition from error free to total loss of all data is relatively quick. There is relatively no "sort of" interfering!
Note that "phone lines" do not exist between exchanges. Message traffic is *trunked* between exchanges! Lines are very distinct from trunks. Either of them is a circuit though...
Fiber of course is not bothered by noise from power lines; but on the other hand fiber itself is an *extremely* noisy media. So much that it is generally unsuitable for analog transmission.
Given another 10 or 20 years, they will no doubt catch up. :-)
How would you judge whether that is true or not?
It's not a matter of feeling this way or that. You don't have enough background to even get the terminology correct, much less have a perspective on the history.
One of the more interesting attributes those of us who started working in the Alaskan telecommunications industry in the 60's or earlier have is that we designed and implemented the entire modern communications system as it exists today. What we started with was essentially a non-existent infrastructure. Everything that exists today, we built without any precedents to force designs based on history. There was *no* privately owned commercial long distance network! There were three different military systems providing for various fighter bases and radar installations, all of which were installed in the 1950's. Few towns had telephone systems, and those that did often had only 1 or 2 long distance lines. We basically started with nothing, and built a very modern system. (A few billion dollars worth of oil being found over here in my back yard didn't hinder that progression at all! ;-)
Hence I've worked on or seen equipment from the 1930s. J, K, L, and O carrier all designed in the 1930's, and some of it installed here during WWII, but most of it immediately post war.
But not having that kind of background is *not* a problem, as long as you don't try to pass yourself off as an expert. For example, I have a little understanding power generation and distribution, and could pontificate on that subject to a few here electricians too... and end up in the same boat you are in on this topic. I make an effort to *ask* them what my experience means, rather than tell them what things appear, to me, to be from my perspective. Several of them here are very good at clarifying the technical details for me!
As above... their use of multipair cable *is* great. Virtually every telephone line is delivered to the customer on that type of cable.
Find some valid documentation and I'll accept your description of the implementation as correct. I say that outside plant multipair copper cable is virtually *all* shielded. The only unshielded cable will be drop wire and customer premise house wiring.
As I stated, it is not a difference in the functionality, merely a matter of how effectively it is implemented. The two types of shields accomplish *exactly* the same thing, but one does it better... at a vastly higher cost.
Your statement above is now something you have contradicted yourself. The local loops are almost *all* analog. That is a far shake from "quite rare nowadays".
I can't see how telecom systems engineers are vanishing either. Their work is much more complex today than it was just 30 years ago...
So? I don't see what your point is?
All you have shown is that telecommunications has become so huge, and so complex too, that it has grown to where it manifests in dozens of ways, rather than only as a simple PABX with a telephone operator to direct calls as needed.
There was a time when I worked in offices where the number of circuits per technician was fewer than 50. Today it is rarely fewer than several thousands.
If you are familiar with research, as opposed to design engineering, it is written in the common vernacular. Why would they, for example, bother mentioning the "load", because that clearly (whatever it is) does not change the conclusion.
Are you a zoologist? If so, why are you working with electronics? The term "aerial", as any decent dictionary should tell you, refers to something relating to air. Cables that are strung on poles are "aerial" cables... not something that radiates like an antenna! Antennas are commonly connected to radios, if you want the radio to be functional.
Regardless of how much fun we can have playing word games, if you actually do design _antennas_ then you *should*, though not necessarily will, have the background to understand the point they made about physical length related to wavelength and its functioning as an antenna.
I'll grant that in theory it would actually act as an antenna at
*any* length; their point was that as the length approaches zero the radiation efficiency also approaches zero. It is an "antenna", but has no value as a useful antenna. (It does have value as a theoretical antenna though, because as the length approaches zero it becomes more and more of a "point source", which is a useful concept to understand too.)
I did all of those things... but it was 40 years ago. Since then I've done digital telephone switching, analog and digital microwave system, fiber optic systems, analog and digital satellite systems, analog and digital carrier systems, data systems, computer administration and software engineering.
One of the benefits of the way it worked here in Alaska was that we all go to do *everything*, if we wanted to.
Who can piss farther.
Ever have a biopsy on your prostate? :-)
-- Floyd L. Davidson Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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