Sync lost on incoming call on 20CN Marconi exchange

I have been chasing a fault with my line (which normally has absolutely minimal errors), whereby when there is an incoming call hundreds of errors are logged in seconds and if we don't answer the phone quickly enough it loses sync. I've now been told it is a 'feature' of Marconi exchanges and there is nothing that can be done about it - I just have to wait for the exchange to be upgraded to 21CN (or fibre).

The more the line is being used at the time, the more likely it is to drop. As I use VoIP on the line this situation is unacceptable.

Has anyone else come across this?

SamKnows shows 21 WBC for September, but the spreadsheet from BT Wholesale doesn't list the exchange - which is the more likely to be correct?

Edited by jelv (Fri 26-Apr-13 12:22:44)

that's not a feature of any ADSL that I've head of. As you said, normally you don't have many errors.

A line fault generating interference from the extra current perhaps, or a device at your end - filter refresh perhaps ?

What has been eliminated:

All recent testing has been from the test socket.
Filter - several been tried - last engineer's visit I gained a filtered faceplate.
Routers - two TG582n's with three different firmware versions
Telephones - DECT and wired. However fault still occurs even if there is no phone plugged in at all!

Last visit the engineer disconnect my master socket and clipped his tester on to the bare incoming wires - still seeing CRC errors when the phone rang.

However the absolute killer fact is that he disconnected my line inside the exchange and connected his tester there - he still saw loads of CRC errors when the line was rung. That eliminates E side, D side and everything at my end.

They've done multiple lifts and shifts.

The response from BTw was that it's a known issue with Marconi 20CN exchanges and I have to lump it!

From some bit loading charts I've seen from other users it looks like Marconi exchanges may not use downstream tones 33-36 which can reduce the maximum sync possible. I'm not seeing an 8128 sync and my attenuation is 21.5dB.

I had that problem on 20CN and PN/OR never seemed to be able or willing to fix it - eventually the only fix was to switch to partial LLU

Edit: SFI inially did a "LIC change" (?) at the exchange which did help a little but after that nothing seemed to be done...

Edited by 4M2 (Fri 26-Apr-13 13:31:10)

perhaps the exchange end filter is the issue, though I would have tried a different breed of router in case something else hangs on better.

If they're saying it's the Marconi exchange does that change if you get 21CN broadband - did 21CN telephony go anywhere in the end ?

21CN broadband is a new DSLAM at the exchange end, just the 21CN telephony part of the roll-out is on hold

I'm confused - Marconi exchange or Marconi DSLAM ? Did BT use Marconi DSLAMs ? Fujitsu and Alacatel I remember from 10 years ago. Then the 21CN ones were Huawei I think.

Can't answer that - all that's been said is 'Marconi exchange'

My exchange is 20CN only (with no LLU either).