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After daily phone line faults at exchange, now DLM has uped Noise Margin

RPMozley
Aspiring Pro
Posts: 1,117
Thanks: 30
Fixes: 5
Registered: 04-11-2011

After daily phone line faults at exchange, now DLM has uped Noise Margin

Well, title explains most of it but here's the detail.
The past couple of days or so our phone line has been cut off due to some major problem at the local exchange. Most of the time the faults occurred at around 10am for some odd reason (10pm one time and not sorted until next day). During the faults there would either be crossed lines with 'number dialed not recognised' message or the annoying sound you get when you forget to hang up but mostly just a dead line.
Anyway, after all that BT OR phone up to check and say that the line is now fixed. That was yesterday and net connection was restored, with an SNR margin of 6db but today I find that the 'brilliant' DLM has now put our line's default SNR up to 9db. Oh, thank you very much DLM but all those lost connections were to do with BT equipment at the exchange and nothing to do with our modem/router dropping the sync on the line.
So basically I'm suck on 9db margin because the DLM won't drop back down to what it was before. I suppose the only way to fix this is to have a SNR reset done on the line, back to the 6 db it should be.
That's RPM to you!!
9 REPLIES
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin

HI RPMozley,
Would you like me to reset it? Bearing in mind it will start a new training period.
Jojo Smiley
RPMozley
Aspiring Pro
Posts: 1,117
Thanks: 30
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Registered: 04-11-2011

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin

Hi Jojo,
Well if that's the only way to get the SNR margin back down to 6db, then I guess I don't have much choice but to go through the retraining again.
Regards,
RPM.
That's RPM to you!!
x47c
Grafter
Posts: 878
Registered: 14-08-2009

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin


Pretty standard and well known problem I'm afraid.
Worse it can occur when BT are fixing someone's line and accidentally disturb another causing multiple re-connections on the other line and in some case yes, the DLM will raise the target margin: - when the other person's line never had any problem on it originally.
The DLM after all is totally unable to distinguish between disconnections caused by a faulty line and one made faulty on a temporary basis by BTOR during their repair work.
No idea about the solution..other than do as it done at the moment which is issue a line/SNR reset on those line affected by it on as as/when/if basis.
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin

Bad luck RPM, hope it goes smoothly.
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin

Hi RPMozley,
sorry I never got back to you yesterday, a few things cropped up. I'll get that done for you now.
Jojo Smiley
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin

Ok,  I have requested your downstream SNR to be set to 6dB. Please allow 24 hours for this to take effect. Smiley
RPMozley
Aspiring Pro
Posts: 1,117
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Registered: 04-11-2011

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin

Thanks Jojo, no problem with the wait. There's plenty of other people for you to deal with more urgently.  Smiley
Hmm... Seems to have happened within minutes of the request being sent @ around 3pm. New sync speed but left with a dead "Connected" PPP connection, which sometimes happens but easily remedied by disconnecting and reconnecting the PPP session.
That's RPM to you!!
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin

Ah good, glad it worked so quickly Smiley
RPMozley
Aspiring Pro
Posts: 1,117
Thanks: 30
Fixes: 5
Registered: 04-11-2011

Re: After daily phone line faults at exchange, now DLM has uped Noise Margin

Just a small update on how things are going so far.
DLM seems to be behaving itself at the moment, in fact it's been very kind recently. In the early hours of this morning it dropped the default noise margin down to only 3db (never seen it this low before) and also removed the interlacing on the downstream (effect seen on ping graph below).
Only issue though is the PN profile hasn't moved one bit so far and is still stuck on 5.2 (sync has remained at above 6210 since reset and currently running stable @ 6775 with the 3db margin).

Edit: Added ping graph for particular day, as original will have passed by once people get to see this.
That's RPM to you!!