Kitz Forum
Broadband Related => Broadband Technology => Topic started by: snadge on June 25, 2012, 12:11:36 PM
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I wondered if anyone could/would offer up some explanation as to how the E-Side wiring works, I recall BS saying something along the lines about them being kept under vast amounts of water...my memory is vague and I cant find the post, but I found this image someone took of the E-Side Pressure Gauges
(https://forum.kitz.co.uk/proxy.php?request=http%3A%2F%2Fwww.line-man.com%2Fforums%2Fuploads%2Fgallery%2Falbum_81%2Fgallery_6301_81_56852.jpg&hash=5a4582fdf1ca24676f2580647277a0dcb75416d5)
hopefully my main man BS will explain when he is not busy :)
thanks
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As I understand it
They are pressurised under air pressure (?9 lbs/sq inch?)
Helps keep out moisture from getting into the cable and will act as advance warning of impending failure if the normal leak rate suddenly increases substantially.
More than that I know nothing - we await BS to add to our knowledge.
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thanks c6em - so they are pressurized in the exchange?
what about the e-side along to the cab? surely that can get 'moist'...?
guess we will have to wait for BS to shed some light on it
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argh.. just lost my long post whilst trying to insert an ascii char and ended up using the back key instead :-X :(
Starts again, but doubts it will be as long.
>>>> Helps keep out moisture from getting into the cable and will act as advance warning of impending failure if the normal leak rate suddenly increases substantially.
Thats my understanding too.
>>> so they are pressurized in the exchange?
I believe so, its a while since I was in the exchange and my memory is hazy on this as I was more interested in the stuff like MSANs... but the cables were pressurised in a dark and dingy dungeon underneath the exchange by a large compressor. TBH its not somewhere to loiter and I seem to recall the engineer saying something about Health and Safety due to the air/gas condition so we only got the briefest of peaks.
>>> what about the e-side along to the cab?
They are pressurised by the equipment in the exchange.. and although the compressor was located in the basement, the monitor dials were in a more easily accessible location, so that any problems could easily be spotted.. ie loss of pressure indicating damage to the cable.
cab <-> e-side cable < -> dungeon where the e-sides are pressurised < -> MDF
↓ ↓ ↓ < - > Pressure gauges for monitoring purposes.
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oh - just found this which helps explain it
http://www.airtalk.com/primer2.html
The cable, although filled with individual conductors and associated insulation, is much like a long garden hose carrying air pressure instead of water. The pressure comes from a mechanical air compressor and dryer, located somewhere near the telephone company cable vault. The compressor supplies the air at approximately 10 PSI, while the dryer removes the residual moisture. Essentially, this means that air with very low humidity is forced into the cables.
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It also means the E-side must be terminated in some 'proper manner' in the PCP with sealing glands at the end to achieve as best as possible air tight seal.
I have hazy recollections something about some PCP's having air pressure guages in them to enable BT engineers to observe the pressure in the E-sides that terminate at that cabinet.
In the exchange as well as the pressurisation connection/sealing gland gubbins on the cable whatever there must be some sort of 'splitter plates' where the 100's of lines in a single E-side cable are progressively split down off the cable into the sub groups of ?25? which are then taken off and further split down before going off to the terminations and spares for future use.
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so the cable with the pairs in all the way up to the cab is full of pressurized air? eeh well I never!!!
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That looks like a picture from telephone house in belfast lol
Gary
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Yes, the E-side cables are pressurised from the exchange all the way to each PCP. I am not sure if every PCP will have a pressure gauge fitted to each E-side cable that terminates there but certainly some PCPs, into which I've looked, have had one or two pressure gauges.
I seem to recall Black Sheep (under his previous ID of razpag) posting the story of how he was a member of a building maintenance team who were responsible for inadvertently taking an entire telephone exchange off the network! ::) They were tasked with running a new copper supply pipe from the air-compressors to the ECP rack and somehow managed to short-circuit the exchange 50 V battery of lead-acid cells, resulting in a bright flash, a loud bang and a totally inactive, silent Strowger exchange.
Ah, I've just found the relevant story. It appears part-way through relatively short thread [1] that had been started by Walter.
[1] http://forum.kitz.co.uk/index.php/topic,9499.msg193292
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so the cable with the pairs in all the way up to the cab is full of pressurized air? eeh well I never!!!
How do you think telephones (never mind ADSL) keep working when the drains flood? ;)
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so the cable with the pairs in all the way up to the cab is full of pressurized air? eeh well I never!!!
How do you think telephones (never mind ADSL) keep working when the drains flood? ;)
@ B'kat - hahaha
seems a bit of an old 'odd' way to ensure cracks in cable sheath dont get worse and keep water out, isnt there some new super strong, super water-tight compound they can use to sheath the cable in..? also... what about the cables from PCP to Ducts and from there to JB's..? seems like "half-a-job" or is a duct also pressurized? theres a good 200m run from the duct to the PCP Iam connected too
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There is one rule with water snadge and one rule only.
IT ALWAYS WINS.
:)
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I've also heard that any duct eventually fills with water.
The positive pressure differential to prevent leakage is used in all sorts of applications as well as cables.
A typical example would be hazardeous process of some form where leakage to the outside environment is not allowed under any circumstances and the process is carried out in a sealed cell. So the inside of the process area is kept at a lower pressure than atmospheric and entry/exit controlled by an air lock. This ensures than any air leakage through any joint is always inwards and not outwards, so no contaminated internal air can ever leak out.
Typical applications are radioactive work and medical/virus research.
You want the opposite in a computer chip assembly clean room environment where the air inside has been highly filtered to ensure it is totally dust etc free. In this case the air pressure in the clean room needs to be higher than external to ensure that no external dirty air can get in but you are no so bothered about the clean air leaking out.
Trying to pressurise a D side set would be too complex.
You would need to run a totally seperate large air line out to each PCP from the exchange to supply the D sides.
There would have to be lots of glands/sealing stuff at the PCP to connect everything up. A PCP may have only have a couple of E sides but lots and lots of D sides.
the D sides have multiple sequential joints in them at each junction box/D.Point....how to seal each of these joints..and continue the air path across the joint. The whole thing would leak like a sieve.
All very messy and complex and taking up a lot of space.
Can you imagine mending a fault - you would need to depressurise the D side,mend the fault at the joint box then try and get a re-seal pressure to hold. You'd be there all day+.
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Snadge -- I've just hunted through a collection of pictures that Walter has kindly provided (over numerous months) and have found a nice example of a PCP with multiple E-side pressure gauges. (If you are really interested, it is PCP number 86 of the Chilworth, Surrey, exchange!)
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@ c6em - thanks for the explanation - appreciated, I see your point, you would have thought in this day & age their would be something better, cheaper and less work than pressurizing air down the cables to keep 'HALF' (up to PCP) the phone lines dry hehe...A-mazing!
@ B'Kat - thanks for trawling out the pic... aye i see, hey amazing like...
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you would have thought in this day & age their would be something better, cheaper and less work than pressurizing air down the cables to keep 'HALF' (up to PCP) the phone lines dry hehe...A-mazing!
I believe that air pressure isnt the only method in use.. but I do seem to recall being told that sometime in the dim and distant past it was a major undertaking for BT to update + pressurise all the e-side cables. Many of these cables had been in the ground since the year dot so it was no easy feat for BT to protect all the e-side cables. I also recall the engineer mentioning that e-sides are seldom, if ever touched. It was probably the best method available at the time, and newer methods used as and when.
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Added
I tried to do a quick google to see if I could find out which year BT started pressurising the e-sides.. I didnt find a date.. but I did find this (https://docs.google.com/viewer?a=v&q=cache:kRzQ5m1vGf0J:stakeholders.ofcom.org.uk/binaries/consultations/copper/annexes/loop.pdf+&hl=en&pid=bl&srcid=ADGEESiRRcWZASefOr7_VVZoWdGp2dyTiZtWNXbOiWuPZhnqwb7J7rrESZRAbJk7jSoNizdw_jjVSjaq2A4Un3R6vxywAhrddnDXrEkbqcTgY-5Dcom-rI-bKlD1wxtCt6IsLchkmN6S&sig=AHIEtbRhTgCXzkELwgiPCC4YjUOScm0stw) which discusses the local loop and cost of upgrading it which you may get some interesting snippets from.
In it theres a lil bit of info about the cables... unfortunately I dont seem to be able to copy the text but look at the end of page 10 and you will see that it states there are also some esides which are gel filled.
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wicked find there kitz!! :)
hey, just thought...FTTC, will that remove the need for these compressed air cables?, is the copper replaced with fibre or is it an add-in?
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Allow me to perform the copy/paste of that section of text . . .
Each PCP is served from the exchange by large cables, typically 500 or 1000 or more
copper pairs. These cables sometimes use pressurised air (supplied at the exchange) as a
means of keeping the cables dry, though there are a variety of alternative technologies too
(e.g. gel-filled cables); pressurised air cables are the option we have costed. These E-side
cables are laid in the E-side duct.
This architecture is illustrated in Exhibit 2.1 below, which shows examples of the cable,
joints, and duct provided.
:)
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hey, just thought...FTTC, will that remove the need for these compressed air cables?, is the copper replaced with fibre or is it an add-in?
:no: No, with FTTC both the D-side & E-side cables are used for telephony and the D-side & FO cables are used for the Internet access.
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haha i was gunna post a screenshot of that diagram...you beat me to it!
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haha i was gunna post a screenshot of that diagram...you beat me to it!
Meow! :P
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Don't know why, but have only just spotted this thread ???
I think over the course of the input here, you've more or less covered it. Just my own thoughts though ......... Equipment Cable Pressure (ECP) racks are designed to pressurise the E-side cables to the Cabinet only. If the Exchange area doesn't have any cabinets, then there will still be a certain section of cable leaving the Exchange that will still be under pressure, and where this then connects to what I'll call the D-side cables, there will be an 'Air block' fitted.
D-side cables are not 'under pressure' (unlike the engineering fraternity ;)), but are grease filled to keep out moisture as much as possible.
The actual compressor can be fitted anywhere within the Exchange, but the read-out dials will be in an equipment room in order to be easily read. The compressors generally have two 'beds', so that whilst one is drying the other is dormant. When they change over 'beds' you know about it, as it's like being stood next to an Articulated Tractor Unit when he applies his air-brakes ....... loud !!!!
I think it was Kitz who mentioned a dark dingy room underneath the Exchange ?? This is called the Cable Chamber and is where all the cables entering the Exchange are neatly formed and presented onto the Main Distribution Frame (MDF) in a neat and orederly fashion. You can imagine how many cables enter our Exchanges, even the smaller ones.
Somebody else commented about pressure gauges in Cabinets (c6em I think ?), which was true. Part of our undertakings when working in a Cabinet, was to view the gauges and report them to the 'Pressure gang' if they were low. They should 'alarm' automatically but hey !! Nowadays they've been replaced by some yellow sealed boxes that I can only assume are telemetry-style devices?? I've no idea how they work or if my observations are correct.
Finally, B*Cat, your memory is damned impressive pal !! You're correct about my dealings with a re-sited ECP rack and the subsequent disaster that ensued. Not my finest hour I can assure you. :-[
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Finally, B*Cat, your memory is damned impressive pal !! You're correct about my dealings with a re-sited ECP rack and the subsequent disaster that ensued. Not my finest hour I can assure you. :-[
Wasn't your supervising TO deemed to be responsible for that mishap? ???
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He was the one held responsible, as it was deemed he should have been supervising us plebs better. But it was carelessness on us T2B's behalf that the incident occured. Should have covered the Wet Lead Acid cells with cardboard, and that would have prevented the accident. One surely does liveth and learneth. :-[
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For any easily confused, this is a pressurised duck
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Don't know why, but have only just spotted this thread ???
I think over the course of the input here, you've more or less covered it. Just my own thoughts though ......... Equipment Cable Pressure (ECP) racks are designed to pressurise the E-side cables to the Cabinet only. If the Exchange area doesn't have any cabinets, then there will still be a certain section of cable leaving the Exchange that will still be under pressure, and where this then connects to what I'll call the D-side cables, there will be an 'Air block' fitted.
D-side cables are not 'under pressure' (unlike the engineering fraternity ;)), but are grease filled to keep out moisture as much as possible.
The actual compressor can be fitted anywhere within the Exchange, but the read-out dials will be in an equipment room in order to be easily read. The compressors generally have two 'beds', so that whilst one is drying the other is dormant. When they change over 'beds' you know about it, as it's like being stood next to an Articulated Tractor Unit when he applies his air-brakes ....... loud !!!!
I think it was Kitz who mentioned a dark dingy room underneath the Exchange ?? This is called the Cable Chamber and is where all the cables entering the Exchange are neatly formed and presented onto the Main Distribution Frame (MDF) in a neat and orederly fashion. You can imagine how many cables enter our Exchanges, even the smaller ones.
Somebody else commented about pressure gauges in Cabinets (c6em I think ?), which was true. Part of our undertakings when working in a Cabinet, was to view the gauges and report them to the 'Pressure gang' if they were low. They should 'alarm' automatically but hey !! Nowadays they've been replaced by some yellow sealed boxes that I can only assume are telemetry-style devices?? I've no idea how they work or if my observations are correct.
Finally, B*Cat, your memory is damned impressive pal !! You're correct about my dealings with a re-sited ECP rack and the subsequent disaster that ensued. Not my finest hour I can assure you. :-[
thanks for the insight BS, mucho appreciated :)