Kitz Forum
Broadband Related => FTTC and FTTP Issues => Topic started by: whatkatedoes on September 20, 2016, 12:54:09 PM
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Hi all, I've been on BT infinity 1 for a year, connected fairly solidly @ 40/8, then in April for the hike to 55 (for an extension in my contract, doh)
Suddenly, around three weeks ago, my sync dropped to 42/6 - I've been trying to figure out what the cause is. I *think* it might be line noise. Scheduled router reboots at 5am can see it return to normal, but only for an hour or so. I've been dealing with the chat support @ BT, and after wading through all the wifi/try different ports on the BT hub I'm not using, they said they would "refresh my line over 48 hours".
This morning, the max attainable rate jumped back to 57.7 (which is generally what it used to be, up to about 60) but I left the router alone. Then at about 1145, it dropped back again to 42. You can see a massive change in the SNRm in the graph here. Anyone any ideas, 55>42 sucks, but actually the drop from 8.5>6ish really hurts in the upload. (Sorry for size, scroll right to see the 1145 "hit")
(https://i.imgur.com/DycJhxj.png)
I've tried swapping back to the HH5, filters, cable (carefully, so as not to trigger DLM myself)
Am wary of BT saying to me "welll.. we only guarantee 29mbit on your line anyway.."
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That sounds very much like crosstalk to me. It would explain the dive in SNRM. :no:
Not much you can do if so. Best thing to do would be to put a DSLStats compatible modem or modem router in and try to pull some stats so that the guys on here can take a look.
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Thanks :) I've got billion 8800nl, and it's hooked up to DSLstats, but really the only thing I understand within is the connection speed and SNRm - so if anyone can advise me what to look for, that would be great :)
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Would my neighbour getting switched from TalkTalk ADSL to BT infinity in the last couple of weeks be a factor in this?
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That looks like a line fault. Is your phone line noisy?
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Not to my ears! It's a cordless, but a decent BT one, and I couldn't pick up anything untoward.
I'm on chat AGAIN just now. Actually I only went on chat after speaking to @btcare about a missed callback last night, they pointed me back at the chat.. and guess what.. I'm having to go through the whole explanation thing again...
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I think you need a wired phone to check properly. I believe cordless phones filter out noise.
You can use the automated checker to see if that can find anything www.bt.com/help/phone
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Shweta: "I can see that there is an fault on the network due to this you are facing this dropping connection and slow speed. We'll need to book an engineer to fix this fault.
I can send an engineer. But if they find the problem is with your home wiring, your equipment, or our network has been damaged within the boundary of your property (by things like trees, building works, corrosion or damp), it’ll cost £129.99."
Hurrah?
We've not changed anything, the only thing changed in our house was the openreach engineer last year coming in to change the wiring a bit, and install a proper faceplate thingie.
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Stats taken from the router around mid-morning when the SNRm was highest, as was the attainable speed:
Max: Upstream rate = 7124 Kbps, Downstream rate = 57629 Kbps
Bearer: 0, Upstream rate = 6700 Kbps, Downstream rate = 42347 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 13.8 7.8
Attn(dB): 23.4 0.0
Pwr(dBm): 11.7 3.8
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It looks just like crosstalk. That drop in snrm is the same size as I get from next doors FTTC. Next door alone take about 12Mb/s of my connection, fortunately other cross-talk sources have a smaller impact but still about 4mb/s down with next largest one. I can tell these sources as they sometimes go on hols or switch off at night.
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Am on good terms with neighbour, so tonight I'll go and have a peek at their router, see what speeds its getting, and maybe even shut it off for a bit to see if it directly affects mine.
I *really* hope that's not what it is :(
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I am running at approximately 40% loss on download and 30% loss on upload due to crosstalk.
On the rare occasion it does improve significantly it is for the likely candidates of 2 weeks or 10d or 1 week so it is clear it is cross talk related to other lines.
I would say my disturbers are spread more like 20% + 10% + 5% + 1% + 1% + 1% + 1% + 1% = 40%
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I managed to find some stats from October last year - it doesn't look like my SNRm has changed much?
04 Oct. DSL Link Up: Down Rate=39994Kbps Up Rate=6490Kbps; SNR Margin Down=6.3dB Up=6.0dB
04 Oct. DSL Link Up: Down Rate=31801Kbps Up Rate=9264Kbps; SNR Margin Down=6.0dB Up=6.1dB
05 Oct. DSL Link Up: Down Rate=39994Kbps Up Rate=6400Kbps; SNR Margin Down=6.5dB Up=6.0dB
05 Oct. DSL Link Up: Down Rate=39996Kbps Up Rate=6493Kbps; SNR Margin Down=6.3dB Up=6.0dB
06 Oct. DSL Link Up: Down Rate=34997Kbps Up Rate=6397Kbps; SNR Margin Down=6.9dB Up=6.1dB
As of right now it's 6.4 down, though up has dropped to 5.5 on a 42/6.7 connection.
*having read up on this a bit*
If it *is* crosstalk.. is it worth trying to cajole the OR engineer to try some pair swaps?
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Yonks back my neighbour let me switch his modem off etc as I thought he was the cause of my cross talk. When he was off my snrm shot up and stayed until he reconnected. Managed a pair swap to get away from him. Someone else is now the crosstalker. It may not pay to get a swap as you could end up with a worse one in time etc..
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Found a snapshot log of a previous resync in effect:
Wed 14 Sep 2016 18:19:25, Noise Margin (dB)= 6.2, Connection Speed (Kbps)= 55000, Upstream NM= 6.1, Upstream Sync= 8004
Wed 14 Sep 2016 18:19:40, Noise Margin (dB)= 6.2, Connection Speed (Kbps)= 55000, Upstream NM= 6.1, Upstream Sync= 8004
Wed 14 Sep 2016 18:19:55, Noise Margin (dB)= -0.7, Connection Speed (Kbps)= 55000, Upstream NM= 5.9, Upstream Sync= 8004
Wed 14 Sep 2016 18:20:10, Noise Margin (dB)= -2.9, Connection Speed (Kbps)= 55000, Upstream NM= 4.7, Upstream Sync= 8004
Wed 14 Sep 2016 18:20:25, Noise Margin (dB)= , Connection Speed (Kbps)= 0, Upstream NM= , Upstream Sync= 0
Wed 14 Sep 2016 18:20:40, Noise Margin (dB)= , Connection Speed (Kbps)= 0, Upstream NM= , Upstream Sync= 0
Wed 14 Sep 2016 18:20:55, Noise Margin (dB)= 6.4, Connection Speed (Kbps)= 42156, Upstream NM= 6.1, Upstream Sync= 6801
Wed 14 Sep 2016 18:21:10, Noise Margin (dB)= 6.4, Connection Speed (Kbps)= 42156, Upstream NM= 6.1, Upstream Sync= 6801
Wed 14 Sep 2016 18:21:28, Noise Margin (dB)= 6.4, Connection Speed (Kbps)= 42156, Upstream NM= 6.2, Upstream Sync= 6801
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Could you give us a look at the QLN and HLOG plots (you should be able to enable collection in settings)? Also, are you uploading to MyDslWebStats?
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The ISP has identified a fault. I'm not sure what else you need?
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Could you give us a look at the QLN and HLOG plots (you should be able to enable collection in settings)? Also, are you uploading to MyDslWebStats?
Yes, I'm k8bit on mydslstats - set it up today.
However, I popped next door, checked their router, was connected 40/6, with a max of.. 40. She turns it off when not in use(!) - and when did the same whilst I was there.. my own attainable leapt back to 57.
:(
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(https://i.imgur.com/yTEeP2S.png)
(https://i.imgur.com/P7gzvoq.png)
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Unfortunately those graphs don't show the whole tone range. If you look under the graphs in DSLstats you'll see sliders labelled Compress ... Expand. You can adjust these to show as much of the tone range as you want, and it's usually best to show all the used tones.
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Unfortunately those graphs don't show the whole tone range. If you look under the graphs in DSLstats you'll see sliders labelled Compress ... Expand. You can adjust these to show as much of the tone range as you want, and it's usually best to show all the used tones.
Thanks - I've updated the images above, hopefully this is correct now?
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Yes thanks, that's good.
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Yes, I'm k8bit on mydslstats - set it up today.
However, I popped next door, checked their router, was connected 40/6, with a max of.. 40. She turns it off when not in use(!) - and when did the same whilst I was there.. my own attainable leapt back to 57.
:(
you just worked it out for yourself right there. That neighbour is your big crosstalker. cont urself lucky they turn their modem off. OR probably won't do a pair swap because of a crosstalk issue.
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I reboot my modem to catch higher sync rates so my noise margin always sits around 4db and I'd probably be happy with it around 2/3db.
As they turn the modem off when not in use just reboot your modem while theirs is off.
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I reboot my modem to catch higher sync rates so my noise margin always sits around 4db and I'd probably be happy with it around 2/3db.
As they turn the modem off when not in use just reboot your modem while theirs is off.
Problem with that is mine will lose sync when they switch on, this can happen at not great times, lol.
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if the snrm drop is so high it's causing a resync every time, and 42 just didn't cut it, you could try somewhere in the middle. perhaps connect when the crosstalker isn't online, but limit the sync speed to say 50mb rather than 55mb. this might be enough to hold the connection steady when your neighbour connects.
It's not the full 55mb, but it's better than 42mb. If you don't know the command to limit the sync speed on your modem then just tell us which modem you use. The command is different for different modems.
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Thanks :) it's a Billion 8800NL.
Noticing the the attainable was up again (ergo neighbor likely switching router off overnight) this morning (as I type) I rebooted the router, and am connected at 55, with an attainable of 58.9.
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adsl configure --maxDataRate 50000 10000 100000
you can send it through DslStats as shown in pic
this will cause a resync and sync at a max of 50 down, 10 up
it saves for every subsequent resync till you reboot the modem
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Wow, Thanks - I'll let you know how I get on :)
Kate
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Or you could get an Openreach technician to fix the fault
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Or you could get an Openreach technician to fix the fault
I suppose that depends on whether or not it will be classed as a fault, or a de facto Fact of Life of current VDSL delivery methods.
I'm a pessimist, so I'm anticipating the worst, and like to be sufficiently armed with The Knowledge regardless.
Anyhoo - Limit applied, sync currently @ 50/7.8, so am waiting for the "hit" of next door, but there's also tomorrow's OR engineer visit, so I feel appropriately ready either way :)
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Hopefully you're ready to plug in your ISPs supplied equipment so the OR guy doesn't just blame your modem, confiscate it and charge you £120? :no:
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Hopefully you're ready to plug in your ISPs supplied equipment so the OR guy doesn't just blame your modem, confiscate it and charge you £120? :no:
Fortunately I'm going to assume that they have a brain, since plugging in the BT hub (which am out of contract for now anyway) changes *nothing*.
Also - the changes made above can be enabled/disabled at the tick of a box.
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Looks like crosstalk to me. Unfortunately both upstream and downstream take a hit at the same time. You may get some temporary relief when they have their router disconnected but thats about it. Last year I did a rough analysis of members of the kitz forums and the average loss per line was ~20Mbps.
At that time my own headline loss was ~25Mbps. About 3 weeks ago another of my neighbours must have got vdsl and I took an immediate 9Mb loss, so my total headline loss is now 33-34Mbps.
Unfortunately there isn't anything that can be done about crosstalk (aside from vectoring). Openreach could swap you to another pair, but it will eventually catch up, which is why they dont like doing so as its only a temporary fix.
Your Hlog looks fine, indicating no physical line fault at the time the snapshot was taken. (Wonders why the graph colours are wrong)
Your QLN graph shows signs of crosstalk especially in D2 (1218-1950). Bumps and curves also in evidence for D3. There's also a nice trough in U2 but its harder to read upstream due to power cut back.
- I tend to compare both QLN and the bitloading graph to give me a better idea.. especially as I was 'brought up' looking for crosstalk before there were QLN graphs so had to look for it on bitload alone.
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(Wonders why the graph colours are wrong)
That's because the band plan in use only goes as far as tone 2100 (or thereabouts). The QLN and HLog graphs cover a much wider tone range, but tones beyond 2100 are shown in blue because they are unallocated.
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d'oh... of course... need to put my brain in gear. Would have spotted that if Id also seen bitload.
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For interest's sake, here we go, rate limit applied, whilst we wait for the big hit.
(https://i.imgur.com/hueo8Pt.png)
(https://i.imgur.com/1OGkvTT.png)
(https://i.imgur.com/K3JCbuC.png)
(https://i.imgur.com/37KNyZP.png)
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hlog is near perfect as Ive seen. The jump at U2 is normal.
PS.. for your info. Hlog shows physical line health/bridge taps as its based on the atten. QLN shows up things like interference and crosstalk.
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hlog is near perfect as Ive seen. The jump at U3 is normal.
PS.. for your info. Hlog shows physical line health/bridge taps. QLN shows up things like interference and crosstalk.
Thank you :) I was nodding obliviously to your original post :D
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edited my post btw. Typo - should have said U2 not U3.... as upstream starts at U0. I did say U2 in the prior post.
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Boom.
Er... what?
SNR Margin (dB) 2.3 3.8
Attenuation (dB) 23.2 0.0
Output Power (dBm) 11.7 3.3
Attainable Rate (Kbps) 43911 7251
Rate (Kbps) 50000 7887
(https://www.speedcheckerapi.com/Images/249244531.jpg)
(Above was taken whilst remoted in, so is not entirely accurate)
So this is showing that the neighbour switched on, my attainable sync took the expected hit to 43.9 - but the router has remained connected at 50. for now!
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Just keep a eye on the error seconds if they creep too high just lower the cap so the line doesn't get hit by DLM.
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Just keep a eye on the error seconds if they creep too high just lower the cap so the line doesn't get hit by DLM.
Total ES Down:1 Up;113
This during the current 5 hour connection period.
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That ES figure is the most important one to watch, but looking at other error indicators can give you a heads-up as to whether things are working well or not. The graphs on MDWS makes it easier to see over time.
I've just checked, using the "last 30 hours" timescale, and can see
- At 11:25ish, when the neighbour's modem was turned on, your downstream SNRM dropped to 2.3dB
- This has triggered no CRC errors, so the ES counter isn't changing [Errored Seconds graph, and B0 CRC Errors graph]
- However, we are seeing FEC errors (ie miniscule, correctable errors) start up - at about 300-400 per minute [B0 FEC graph]
- And G.INP retransmission is being pushed a little harder [G-Retransmit Tx graph]
Both FEC and Restransmit-TX have started showing spikes since 16:30, so I'd suggest that a careful watch is needed to make sure the ES rate doesn't suddenly start to climb (especially as it gets dark).
If it starts to go up much, you want to alter your speed-limit down a notch. A downstream SNR of around 3dB seems to be the point where errors become more plentiful.
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Glad that worked for you. As others have said you can now tweak that up/down to suit. You've achieved the 1st goal of maintaining sync when the neighbour connects. Now you need to keep an eye on errors, the ES rate in particular. If they start to get too high I would be aiming more for a dip to 3dB than 2.3dB.
Or you could get an Openreach technician to fix the fault
With his line resyncing every time the neighbour connects it shouldn't be too hard to get a pair swap. It could end up being worse though. At least at the moment his disturber turns their modem off for large periods of time.
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Engineer update: lovely guy... but completely oblivious to the issue of crosstalk. Decided to be open with him and mention up down nature of neighbours router. He thinks this would not be an issue.
Am not feeling all that confident, lol
When he gets back from cabinet excursion ill see if i can get the neighbour to switch their router off...
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So he was here for about 3 hours. Changed some stuff outside, fitted an nte5? Face plate. Speeds are now holding at 55 even when neighbour connects...but i can see is struggling .. so i might throttle to 52 or something.
Max attainable when neighbour off has risen to 60.
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It's holding at a speed of 55Mbps, but with an SNRM that has dropped to 1.4dB. On MDWS, you can see the consequences on the FEC rate, and the retransmission rate (both very noticeable). It has now started to register on the ES rate.
Since 01:10, there has been a sharp increase in both FEC rate and retransmission rate, I'd be getting worried about a marked increase in ES's soon.
Definitely worth dropping speed somewhat.
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It may be worth getting your neighbour to try a brand new router, if they have an old one causing interference.
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Would my neighbour getting switched from TalkTalk ADSL to BT infinity in the last couple of weeks be a factor in this?
How old could it be? I assume they were sent a new BT Hub when they switched.
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It's not unheard of for BT Hubs to be faulty
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@whatkatedoes
I think you've set the speed limit to 53Mbps now. Probably a good choice - it gives the line a little more room for resilience.
Although there was a lot of errors on the line last night, the FEC and retransmission processes handled them really well, so the ES rate stayed well under control. It looks like you've got things under control as far as this neighbour is concerned.
Don't forget that other disturbers could be added at any time, so this is a thing to keep an eye on in future.
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Yeah i decided this morning to try 53 to see how it held. We're not at home this weekend so its all being observed/tweaked remotely!
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Throttled back to 52 after a drop on Monday, we'll see how that goes.
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Just to say a big THANK YOU to all in this thread - have managed to stabilize sync @ 52500/7.7 due the advice given here - up from the drop to 42/6 :)
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You're very welcome
If you run DslStats constantly it can be set to automatically send the maxdatarate command when it detects no DSL connection. This can be handy for occasions where the modem may reboot itself, preventing it syncing at the full rate which is causing problems.
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So, this is a bit of a post-necro'ing, but I thought it might be interesting for some.
Recap: My FTTC was rated @ 35-57 down 4-7 up in the line checker back when I first got it installed. Using the BT "free" upgrade my infinity1 sat nicely at 55/7 typically. But then, my neighbour got connected.. and that caused my connection to resync to 43-45. They switched their router off at night, which allowed my router if rebooted to sync back at 55, until next they switched on. Through advice in this thread, I was able to throttle sync to a stable 52 succesfully for quite some time. Eventually though, I got re-banded to I'd guess 50, as sync would lock at 49997 or some such, and that was that.
2 months ago, fleeing another price hike, I switched to plusnet unlimited/uncapped. DLM released me, and I initially connected at 57, but neighbours soon put a stop to that, and I'd get dropped to 45, I tried to catch them during off periods and reinstate the throttling of before.. but it just would not work for some reason. Alarmingly, when I checked the line speed estimator, it now showed my line capable of 40mbit at best.
Then something odd happened after a few days, I resynced at 50.. and neighbours rebooting router no longer affected me. Long story short.. Vectoring got enabled.
A week later, and here's where we're at:
Dn Sync: 67, max attainable: 72.
Sync has been rising throughout the week, I thought I was doing good at 57, then it was 62, 65, and now 67, every few days a resync higher. I just wish my upstream was better :(
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What a difference G.INP & XdB with Vectoring does to ones BDUK line :)
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@Kitz, how can you find out if you are on a BDUK line?
Sent from my SM-G930F using Tapatalk
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Use the instructions for Cabinet Lookup info (http://www.kitz.co.uk/adsl/cabinet-lookup.htm#fttc_cab_info)
It should tell you on the results for your cab on there eg
Phase BDUK Lancs 12b
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Thanks, so it looks like in am on the following - Phase BDUK Lancs 10b.
So what benefits should that entail, if any?
Sent from my SM-G930F using Tapatalk
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That you may get Vectoring