I've seen the other responses to the thread.

I too believe that it is possible especially if there is a low impedance fault - not quite a short circuit but conduction through water or deposits on terminals. That could drastically alter the load impedance of a filter and totally change the characteristics. However, without seeing the design of the filters in the cabinets it will be hard to say definitely.

An unequivocal NO is certainly not the right answer

Surely the loop start / ground start signalling gets passed through the cabinet, otherwise how does the switch know when you pick the phone up?

that's DC, even the lowest of low pass filters should let that through.

An unequivocal NO is certainly not the right answer

But it is 99.9% right. Nothing is ever completely cut and dried when it comes to ADSL/VDSL faulting. In 2.5 years of working on this stuff, even when a line fails it's PQ test due to an E-side, and it is duly swapped out, this has never made an iota of difference to the results on the VDSL.

However, without seeing the design of the filters in the cabinets it will be hard to say definitely.

So whilst applying informed logic to your answer, mine was based on experience.

Hence in the Splitters, it is VHF/UHF Reject filters in the Phone leg, whilst the ADSL leg is "straight-through", ie no filtering.

As ADLS and VDSL both operate in the short wave and AM bands the split between pass and rejection is a lot lower than that.

See the relevant BT SIN, the specs are all in the public domain:

The insertion loss when the attached telephone is off hook between 100 Ohm source
and loads at Line and Telephony Ports should be greater than 29 dB at 32 kHz and
greater than 55 dB from 200 kHz to 1.104MHz. (2.208 MHz for ADSL2+).

Here's a splitter spec too http://ww2.pulseeng.com/products/datasheets/B899.pdf

Edited by yarwell (Sun 19-May-13 11:36:16)

I'll accept it is unlikely but it could happen.

Don't forget my experience is based on nearly 8 years designing telephone switches and line cards for various environments.

In reply to a post by MHC:

I'll accept it is unlikely but it could happen.

Don't forget my experience is based on nearly 8 years designing telephone switches and line cards for various environments.

I don't even really understand how balanced pair signal transmission works

i do recall thin wire ethernet not working if the termination resistor was removed, presumably the same thing would have happened with a short rather than an open circuit.

I'll accept it is unlikely but it could happen.

I suspect we are basically saying the same thing, it *could* happen, but is hugely improbable, hence my 99.9% answer, no.

Don't forget my experience is based on nearly 8 years designing telephone switches and line cards for various environments.

You know I know that.
If you want to make some serious spons, and cheer up a lot of CSE's, make and supply a cheap line card to replace the current system X and Y stuff which is falling over as we speak. NDT, OWT and BNR faults abound, I'm sick of getting the damn things swapped out.

One of the principal designers of the X line cards worked with me for a couple of years. At times I wanted to strangle him! He currently lives in Taplow.

He currently lives in Taplow.

Close enough, he's a marked man.
I'd ring him and moan, but his voice service is most likely OOS at present !

Anyhoo, we are drifting OT here.

His phone number is: 01628 6xxxxx


Anyway ... England are all out so I had better go and finish cutting back some 40' conifers - down to 20' WITHOUT ripping out the drop wire that runs through.

Edited by MHC (Sun 19-May-13 11:49:56)