ADSL loses sync in the middle of phone calls

Hi guys,

This is a bit of a strange one. I've got an ADSL connection that has worked flawlessly for 6 months where the sync averaged 19000 kbps / 2500 kbps - and I've had a continued 18Mb/2Mb service.

During that time, the phone line was never used for calls, it didn't even have a phone attached.

Just this week, I started to use the BT phone line the ADSL service is provided on as I needed a second line. It has simple wired phone attached. What I have done in order to free up the Vonage VOIP line for outbound calls, is to divert all calls the BT line. This works just fine (but could well be introducing this weird issue).

Since starting to use the phone, after receiving the first phone call, about 10 minutes into the call, there was a static/interference noise over the phone and the ADSL connection lost sync. About 1 minute later, the line re-synced at 16470 kbps / 1591 kbps - an immediate 3Mb drop.

Then I received a second phone call, about 10 minutes into the call, there was static noise on the phone and again, the ADSL line lost sync. 1 minute later, it re-synced at 10822 kbps / 1902 kbps. Then another 15 minutes later (during the same phone call), there was static noise over the phone and the line lost sync again. 1 minute later, it re-synced at 4944 kbps / 1664 kbps.

I'm trying various tests from a mobile phone direct to the line (not via the call divert), to see if the same things happen, but so far, not.

I have called the BT line test (17070) and run a quiet test 5 times for the maximum time and there was pure silence.

I know the best answer is to stop using the phone line - but I wouldn't mind actually fixing it and being able to use the line. But having a reliable and fast internet connection is 100% paramount.

The current line stats are:

noise margin upstream: 8 db
output power downstream: 17 db
attenuation upstream: 16 db

tone 0- 31: 00 00 00 05 68 89 9a aa aa aa aa aa aa aa aa aa
tone 32- 63: aa aa ab bb ba ba ab aa aa aa aa aa 00 00 00 00
tone 64- 95: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 96-127: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 128-159: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 160-191: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 192-223: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 224-255: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

noise margin downstream: 18 db
output power upstream: 13 db
attenuation downstream: 26 db

tone 0- 31: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 32- 63: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 64- 95: 44 45 55 55 55 55 55 55 55 55 55 55 55 55 55 55
tone 96-127: 55 55 66 66 66 66 66 66 66 66 66 66 66 66 66 66
tone 128-159: 66 66 66 66 66 66 66 66 66 66 66 66 66 66 66 66
tone 160-191: 66 66 66 66 66 66 26 66 66 66 66 66 66 66 66 66
tone 192-223: 66 66 66 65 55 55 55 55 55 55 55 55 55 55 55 55
tone 224-255: 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55
tone 256-287: 55 55 55 55 55 55 55 55 55 54 55 44 44 44 44 44
tone 288-319: 44 44 44 44 44 44 44 44 44 44 44 44 44 44 44 44
tone 320-351: 43 33 33 33 33 33 33 33 33 22 22 22 22 22 22 22
tone 352-383: 22 22 22 22 22 22 22 22 22 22 22 22 11 11 11 11
tone 384-415: 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
tone 416-447: 11 11 11 11 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

To add a little more information.

I called the line directly and there was no loss of sync for a 30 minute phone call.

I then called the Vonage number, which diverts to the line, and after 15 minutes, the line had dropped sync, but this time re-synced at 16433 kbps / 1902 kbps

So it seems to be an issue with Vonage call divert and the BT line - but I've no idea how they are related.

To add some more information.

I called the line directly again and within 10 seconds, there was considerable static on the phone, and the ADSL connection lost sync, then the line re-synced at 7223 kbps / 1902 kbps.

I then ran a quiet line test straight away, and there was still considerable static/noise and the ADSL connection dropped sync 2 further times during the call.

So I now know it has nothing to do with call diverting on Vonage.

I have replaced the RJ11 cable and microfilter and moved the modem and phone as far away from any electrical equipment as possible to rule out interference from the nearby firewall, wifi router, vonage VOIP box, server and phone PBX.

Its probably something to do with the bunch of equipment and wiring all in close proximity and its only been highlighted by the recent use of the phone line.

Here is the ADSL line stats after re-sync and moving the phone + modem.


noise margin upstream: 13 db
output power downstream: 21 db
attenuation upstream: 16 db
tone 0- 31: 00 00 00 02 57 9a bc cd dd dd de ee ee de ee dd
tone 32- 63: dc cb bb bb bb aa aa aa 99 99 99 88 00 00 00 00
tone 64- 95: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 96-127: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 128-159: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 160-191: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 192-223: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 224-255: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
noise margin downstream: 9 db
output power upstream: 15 db
attenuation downstream: 26 db
tone 0- 31: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 32- 63: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 64- 95: 99 ab bb bc cc cd dd dd dd dd de ee ee ee ee ee
tone 96-127: ee ee ee ee ee ee ee 0e ee ee ee ee ee ee ee e0
tone 128-159: ee ee ee ee ee ee ee ee ee ee dd de ed dd dd dd
tone 160-191: dd dd dd dd dd dd dd dd dd dd dd dd dd dd 0d d0
tone 192-223: dd dd dd dd dd dd dd dd cd ca dd dd dd dd dd cc
tone 224-255: cc dc dd cc cc cc cc cc cc c0 cc cc c2 cc dd cc
tone 256-287: bc cc cc cc cc cc cc cc cc cc cc cc dc ac cc cc
tone 288-319: cc c0 cc cc bb bc cc cc cb bb cc cc cc cc cc cc
tone 320-351: cc cb bb bb bb bb bb bb ba 5a bb bb bb aa 0a aa
tone 352-383: aa aa aa aa aa aa aa 99 99 99 99 99 99 99 99 98
tone 384-415: 99 99 99 99 99 99 99 98 88 88 88 88 88 88 88 88
tone 416-447: 88 78 88 88 88 88 78 77 77 77 77 77 77 77 77 77
tone 448-479: 77 77 76 77 66 66 66 66 66 56 66 55 65 55 55 55
tone 480-511: 55 55 55 55 55 55 55 55 55 55 55 55 55 44 54 45
LAN Information:
IP Address: 192.168.1.1
IP Subnet Mask: 255.255.255.0



More testing to follow.

Edited by deleted (Fri 18-May-12 11:53:14)

Could it be a line fault which has only come to light as it has been carrying the ring current for the first time in a long time?

Who is your ISP and who is the phone line provider?

If you can consistently show the line being dropped when receiving a call then a decent ISP may be moved to get BT OR to look at it.

Of course, ultimately, you may end up with a charge for this if they claim to find anything wrong with the voice line.

Phone line provider: BT
ISP: Talk Internet (not to be confused with talk-talk)

I've re-wired the entire cupboard that all the electrical kit is in, made up completely new RJ11 cables that are just the right length (no bundled up wires), no power cables crossing over or near phone line/RJ45 cables.

It seems to be better now, at least the first few tests I've done have been good so far. The microfilter > modem RJ11 cable is now 5cm long and the modem is wall mounted next to the phone socket, so there isn't any scope for interference on that cable

I'll see how things go now, but it does seem to be better. It could well just have been interference from electrical wires/transformers/phone PBX/server/router etc.

Well, that was short lived.

Despite the modem being at least 12" away from the nearest piece of electrical equipment, all wires replaced and no power cables crossing phone cables - the issue persists.

It had been fine for about a week, then all of a sudden today the ADSL line dropped 3 times during 1 phone call.

Have you tried a different phone? I had an issue where an old phone was sending noise down the line when in use

Other than this the problem is NOT your equipment or the close proximity of the wires! Plenty of people have the master sockets behind TV stands with sky boxes, landline and broadband all connected to the socket and no issues.

I think a BT engineer needs to visit and resolve the issue.

I've tried a few phones now, wired, wireless and the phone PBX itself. But it doesn't seem to make a difference.

The only thing I haven't tried is another modem. So I'm going to order another modem and see if that makes any difference - and failing that, I'll have to get BT out.

I'm not sure why I bother paying BT extra for the "Enhanced Care" service when it seems I have to do all the diagnosing myself.

In reply to a post by ben_uk:

I've tried a few phones now, wired, wireless and the phone PBX itself. But it doesn't seem to make a difference.

The only thing I haven't tried is another modem. So I'm going to order another modem and see if that makes any difference - and failing that, I'll have to get BT out.

I'm not sure why I bother paying BT extra for the "Enhanced Care" service when it seems I have to do all the diagnosing myself.

The enhanced care service is for line faults before the NTE, its a responce time service not a "you don't have to check your own kit first service."

Yeah, I understand that.

It makes me laugh that it is an SLA'ed service, but the diagnosing alone can take a few days - which makes the 4hr priority response a bit moot.