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Standard User WWWombat
(regular) Tue 15-Mar-11 14:52:54
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Re: Got FTTC? How is the master socket configured?


[re: Goza] [link to this post]
 
In reply to a post by Goza:
I don't think I've done anything contrary to BT's intention really; the openreach installer offered the option of an extension (up to 30M I think) from the master socket.

The general thoughts are that having a long RJ11 lead, particularly a long flat lead, is bad for the sync speed. The length of cable between the master socket (with filter) and the modem, if done in flat, cheap, untwisted cable (like most RJ11 cables), is a significant source of errors on the line.

The trick, then, is all about managing the likelihood of collecting interference on this line. And the BT data extension, I guess, is designed to manage this well. If you've got good quality cable in there, then it probably isn't an issue.
Standard User meditator
(fountain of knowledge) Tue 15-Mar-11 17:51:46
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Re: Got FTTC? How is the master socket configured?


[re: WWWombat] [link to this post]
 
Wombat, before you posted your last submission about the length of the RJ11 lead, I'd been thinking about exactly the same issue. However, I came to the conclusion that unless any unfiltered extension coming away from the master socket is done with extraordinarily ropey cable, any such extension should make no difference to the performance of the line. Think about it: the copper line going all the way back to the cabinet is in all probability going to be in far less shape than any extension you fashion at the NTE5, and that copper line won't have as many twists in it and therefore be as good at interference rejection as any Cat5 cable you use. Any unfiltered extension you add is merely that - an extension of a few metres of what is already a few hundred metres of cable going back to the DSLAM. So, I don't see why there's apparently such a passion for BT techies to install the modem right by the NTE5.

The only remotely plausible reason I could come up with is that BT may be trying to maintain as uniform a 'transmission line' from the DSLAM as possible, so as to achieve the very best sync speed and reduce the number of retransmissions due to distortion s of the signal. This sort of consideration will become more important at the higher speeds of FTTC. This would not, at least in theory, be achieved if you added an unfiltered extension off the NTE5 and then ran the modem off the extension, as the NTE5 and its internal components would then represent a geometry discontinuity in the transmission line and would theoretically cause reflections and other electrical distortions of the FTTC signal. But I suspect that if any such negative effects do occur at all, they'd be minimal. You'd not get really bad distortions of the signal unless you formed two or more very long extensions or 'spurs', say two that were 5 or 10 metres each, or even more. This is, in fact, one good reason why starred arrangements will become a bit of a no-no with FTTC.

I'm inclined to think, though, that the real reason for BT wanting to connect at the NTE5 rather than at an extension is that, if they do the latter, they cannot then guarantee the customer the complete integrity of the line, since the master socket will have now been shifted some way back down the line.
Standard User kamelion
(experienced) Tue 15-Mar-11 19:58:38
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Re: Got FTTC? How is the master socket configured?


[re: BatBoy] [link to this post]
 
and a knife

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Standard User BatBoy
(legend) Tue 15-Mar-11 20:05:03
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Re: Got FTTC? How is the master socket configured?


[re: kamelion] [link to this post]
 
and some WD40



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Standard User WWWombat
(regular) Wed 16-Mar-11 00:22:21
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Re: Got FTTC? How is the master socket configured?


[re: meditator] [link to this post]
 
In reply to a post by meditator:
Wombat, before you posted your last submission about the length of the RJ11 lead, I'd been thinking about exactly the same issue. However, I came to the conclusion that unless any unfiltered extension coming away from the master socket is done with extraordinarily ropey cable,

The short answer is that you may be under-estimating the spec of the BT overhead drop cable back to the DSLAM, and under-estimating the impact that your house can have on the signal.

I can't explain it better than this page at ADSL Nation.

Note that the untwisted pairs will not be able to reject any interference, and your house is full of it - especially if your cable runs anywhere close to mains.

Remember that, in most modern BT installations, the #4 wire (bell wire) is effectively used alone, so is effectively untwisted. This wire, running out to extensions, catches a lot of this interference around the house and can inject this into the ADSL signal. It is no coincidence that BT's i-Plate (which disconnects the bell wire) advertises an average speed gain of of 1.5Mbps - its because of the interference within the house.

I was really responding to this part of Goza's statement:
so all I did was to run a long RJ11 to RJ11 cable from the master socket to my router location where I moved the modem. The cable is thin and was easy to hide and handle all the way. It works a treat. I used a ready made one and hid the slack but it would have been easy enough to make one. You have a choice of flat or round cable as well (I used flat).

to try to make sure that Goza wasn't using some ropey old RJ11 wire wink

In reply to a post by meditator:
The only remotely plausible reason I could come up with is that BT may be trying to maintain as uniform a 'transmission line' from the DSLAM as possible, so as to achieve the very best sync speed and reduce the number of retransmissions due to distortion s of the signal.

You might be right. Certainly it seems more important that the VDSL signal is split off before the telephony side enters any kind of star arrangement. It might not be important now, but it could be down the line with greater cable-fill and higher crosstalk levels.

Or it might just be to reduce the likelihood of future callouts - or at least to ensure you can be charged for such callouts.

In reply to a post by meditator:
I'm inclined to think, though, that the real reason for BT wanting to connect at the NTE5 rather than at an extension is that, if they do the latter, they cannot then guarantee the customer the complete integrity of the line, since the master socket will have now been shifted some way back down the line.

I'm not sure about that.

One of my lines is wired in an interesting way: the cable comes into the house, arrives at 1 socket, and then passes through the other sockets in a linear fashion (no stars). However, the *last* socket is the master.

The external BT line passes up through the sockets on a spare pair, then the internal signal passes back down through the same sockets on the normal 3/4/5 connectors. This was wired this way by a BT engineer when I first had ADSL installed, prior to there being a self-install option.

I'm not sure if Openreach engineers would still install a line in this way today. Certainly there's plenty of opportunity for me to much up the integrity of that line!

Edit: To clarify who shouldn't be using the ropey old RJ11 cable!

Edited by WWWombat (Wed 16-Mar-11 00:27:34)

Anonymous
(Unregistered)Wed 16-Mar-11 00:50:16
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Re: Got FTTC? How is the master socket configured?


[re: WWWombat] [link to this post]
 
In reply to a post by WWWombat:
The external BT line passes up through the sockets on a spare pair, then the internal signal passes back down through the same sockets on the normal 3/4/5 connectors...

I'm not sure if Openreach engineers would still install a line in this way today.

From the description here, I believe that's exactly what the Openreach engineer did!

JC
Standard User meditator
(fountain of knowledge) Wed 16-Mar-11 11:44:42
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Re: Got FTTC? How is the master socket configured?


[re: WWWombat] [link to this post]
 
You make some good points in your response, Wombat.

I would agree that the home environment is a fairly noisy place, electrically speaking. It'll vary from household to household. But at least something can be done about the extension wiring if it isn't up to scratch, whereas the long length back to the cabinet will remain as is. Much of this country's underground suburban telephone cabling is more than 50 years old and is in a pretty bad way. Perhaps, for overhead cabling, to a lesser extent. It certainly is around here, anyway, and was of course put in the ground in the voice-only era, so crosstalk and interference weren't as critical then as they are today.

I wouldn't say that the outdoor environment is necessarily any cleaner than the indoor one, as underground cabling invariably passes by the electrical cables of successive street lamps, can run within just a few metres of massive buried local electricity supplies (as recently installed under the main road around here), and are subjected to constant electrical interference from vehicle ignition systems, mobile phone signals, radio and TV signals, civil works electrical gear, etc. The outdoor phone cabling will be affected to varying degrees by these.

My view is that if you use something like CW1308 indoors as the very minimum, and you lay out the run as linearly as possible, then it's not going to be any worse than that great length going out of the house back to the DSLAM. In terms of crosstalk at the user end, in fact, it should be a whole lot better.

Using an XTE-2005 plug-in at the NTE5, I myself will be running a length of Cat5e, about 12m worth, terminating in either an XTF85 or an RJ45 socket. The VDSL modem can then be plugged into that via the usual 1 metre patchlead. This extension, though carrying the FTTC signal, will have similar rejection performance to the Ethernet cabling on the output side of the modem (and between router and computer, if it's a 'wired' computer connection).

Whether or not the BT techie, when the day comes, will agree with this remains to be seen. If he/she doesn't, he/she will just have to install the modem by the master socket in my living room. My plan, however, is to organise a contingency extension, about which the BT techie should have no qualms at all. If I do that right, I'll not end up stuck with the modem in one place and all my computer stuff in another and no quick, neat and permanent means to get between the two.

I suspect a lot of subscribers will find themselves in a similar position as, years ago, the positioning of master sockets by BT in their homes may have been satisfactory then but will almost certainly be completely unsatisfactory now. So, for anyone with the requisite skill and tools, I'd advocate that they carefully plan their new in-home FTTC topology and install a ready-to-use unfiltered extension well in hand.
Standard User RobertoS
(sensei) Thu 17-Mar-11 09:25:21
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Re: Got FTTC? How is the master socket configured?


[re: Anonymous] [link to this post]
 
In reply to a post by Anonymous:
In reply to a post by WWWombat:
The external BT line passes up through the sockets on a spare pair, then the internal signal passes back down through the same sockets on the normal 3/4/5 connectors...

I'm not sure if Openreach engineers would still install a line in this way today.
From the description here, I believe that's exactly what the Openreach engineer did!

JC
Your link doesn't work for anyone in threaded mode, and a swap from there to Flat just takes you to the opening post of that thread. Might not even work in Flat mode if the reader's page settings are different from your.

You should always copy the "link to this post" in the header. The correct link is this smile.

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