I've been told by several people (including a BT engineer) that ADSL can
work on just one wire. Whenever I heard this, I thought "Hmm, really?",
and not thought about it any more.

It now appears to have happened to one of our lines. The phone is dead,
but the ADSL works great. BT say it's a line break, and will take up to
two weeks to repair (yes, it's a business line with TotalCare on it -
they did respond in 4 hours, but won't be fixing it for a while ;-).

We have two other lines, but they're both ISDN.

So, what's the mechanism that allows me to get 1M down a single wire?


--
Grunff

Grunff wrote:
I've been told by several people (including a BT engineer) that ADSL can
work on just one wire. Whenever I heard this, I thought "Hmm, really?",
and not thought about it any more.
snip
So, what's the mechanism that allows me to get 1M down a single wire?

Basically, the losses at voice frequencies, and DC may be tens of thousands
of times less than at the higher frequencies used for ADSL.
Especially, if the line was good beforehand.
For example, if really close to the exchange, 20db of losses across the board
will make voice unusable, but will only be noticable if you look at the
router status page for losses.

On Sat, 18 Dec 2004 12:37:21 +0000, Grunff strung
together this:

So, what's the mechanism that allows me to get 1M down a single wire?

Without getting too tecnical, as I can't recall it all off the top of
my head, ADSL works on a RF frequency so can 'jump' small breaks in
the cable.
--

SJW
Please reply to group or use 'usenet' in email subject

In article ,
Grunff wrote:
I've been told by several people (including a BT engineer) that ADSL can
work on just one wire. Whenever I heard this, I thought "Hmm, really?",
and not thought about it any more.

It now appears to have happened to one of our lines. The phone is dead,
but the ADSL works great. BT say it's a line break, and will take up to
two weeks to repair (yes, it's a business line with TotalCare on it -
they did respond in 4 hours, but won't be fixing it for a while ;-).

We have two other lines, but they're both ISDN.

So, what's the mechanism that allows me to get 1M down a single wire?

IIRC, it's on an RF carrier, so doesn't need a DC path.

Have you checked for DC on the incoming line? That would show if it's
intact to the exchange.

--
*Can vegetarians eat animal crackers?

Dave Plowman London SW
To e-mail, change noise into sound.

On Sat, 18 Dec 2004 12:37:21 +0000, Grunff wrote:

but the ADSL works great. BT say it's a line break, and will take up
to two weeks to repair (yes, it's a business line with TotalCare on
it - they did respond in 4 hours, but won't be fixing it for a while
;-).

I'd be jumping up on down on succesive supervisors to get it fixed
PDQ. When I asked one of the local engineers about Total Care he said
that they would be down holes in the ground 3AM Christmas morning if
they had to do so to repair a Total Care line...

Still think of the compensation for two weeks lack of phone service on
a business line... B-)

If it was the ADSL that was dead I could understand the delay but as
it's the main voice service that is AWOL that should be sorted really
quick.

--
Cheers
Dave. pam is missing e-mail

If you are on a Total Care line then they should fix it or start taking
active steps to do so ASAP. You should escalate the fault higher and higher
until they sort it. ADSL needs two wires to work properly.

Peter Crosland

On Sat, 18 Dec 2004 16:50:40 -0000, "Peter Crosland"
strung together this:

ADSL needs two wires to work properly.

But not to work.
--

SJW
Please reply to group or use 'usenet' in email subject

ADSL needs two wires to work properly.

But not to work.

Care to explain that? Unless two wires are connected the link will not
function at all.

On Sat, 18 Dec 2004 19:04:10 -0000, "Peter Crosland"
strung together this:

Care to explain that? Unless two wires are connected the link will not
function at all.

See my other post. ADSL is carried at a radio frequency (RF) so will
effectively 'jump' gaps in cables.
It does work with one wire only connected without any problems and in
some cases can work with none.
For an electrical current to flow you are quite correct though.
--

SJW
Please reply to group or use 'usenet' in email subject

"Grunff" wrote in message
...
I've been told by several people (including a BT engineer) that ADSL can
work on just one wire. Whenever I heard this, I thought "Hmm, really?",
and not thought about it any more.

Only at a pretty poor performance, if you are near the exchange and there is
a lot of capacitance to earth at both ends. ADSL depends on balanced lines
to reject interfering noise, but the error correcting codes also do the same
job so you will get some throughtput anyway.

The ADSL signal works in a series of 4kHz slots from 30kHz up to over 1MHz.
Lower slots can encode up to 10 bits whereas higher slots only usually
manage 1 bit. But on a perfect system with a short piece of wire ADSL can
manage over 8Mbps so getting 1Mbps (if you are actually getting that even)
isn't too arduous.

But are you sure the break isn't in your splitter filter in which case the
ADSL is getting both A and B lines correctly.

Care to explain that? Unless two wires are connected the link will not
function at all.

See my other post. ADSL is carried at a radio frequency (RF) so will
effectively 'jump' gaps in cables.
It does work with one wire only connected without any problems and in
some cases can work with none.
For an electrical current to flow you are quite correct though.

You are being somewhat disingenuous on this matter. In theory ADSL may work
but in practice in such a case the signal to noise ratio is likely to make
the link very unreliable with lots of drop outs. The bottom line is that an
ADSL line will only function correctly if the telephone circuit is in good
order.

On Sat, 18 Dec 2004 22:22:22 -0000, "Peter Crosland"
strung together this:

You are being somewhat disingenuous on this matter. In theory ADSL may work
but in practice in such a case the signal to noise ratio is likely to make
the link very unreliable with lots of drop outs. The bottom line is that an
ADSL line will only function correctly if the telephone circuit is in good
order.

That's what I said. It does work in practice, sometimes.
--

SJW
Please reply to group or use 'usenet' in email subject

Dave Liquorice wrote:

I'd be jumping up on down on succesive supervisors to get it fixed
PDQ. When I asked one of the local engineers about Total Care he said
that they would be down holes in the ground 3AM Christmas morning if
they had to do so to repair a Total Care line...

I do a lot of jumping when this happens (2-3 times a year), still
doesn't actually achieve anything. Last time I did so much jumoing we
had a visit from the BT regional manager. Didn't actually achieve anything.


Still think of the compensation for two weeks lack of phone service on
a business line... B-)

Lat time we had 2x ISDN (two separate pairs) lines down for 11 days. I
think it was about £300 compensation. I can't even begin to calculate
the cost to us :-(


If it was the ADSL that was dead I could understand the delay but as
it's the main voice service that is AWOL that should be sorted really
quick.

In /theory/.


--
Grunff

Mike wrote:

But are you sure the break isn't in your splitter filter in which case the
ADSL is getting both A and B lines correctly.

No, break deff. on the line.

--
Grunff

Dave Plowman (News) wrote:

Have you checked for DC on the incoming line? That would show if it's
intact to the exchange.

Just did this now - I don't know what it's supposed to be, but I get ~2V
DC. What does that mean?

--
Grunff

Peter Crosland wrote:
If you are on a Total Care line then they should fix it or start taking
active steps to do so ASAP. You should escalate the fault higher and higher
until they sort it.

As in my reply to Dave L, it just doesn't help. They are totally
useless, and don't know the meaning of customer service.

--
Grunff

On Sun, 19 Dec 2004 08:35:17 +0000, Grunff wrote:

Dave Plowman (News) wrote:

Have you checked for DC on the incoming line? That would show if it's
intact to the exchange.

Just did this now - I don't know what it's supposed to be, but I get ~2V
DC. What does that mean?


There should be about 50v DC so it means that one or both legs of the
line are class F.





--

..andy

To email, substitute .nospam with .gl

"Grunff" wrote in message
...
Dave Plowman (News) wrote:

Have you checked for DC on the incoming line? That would show if it's
intact to the exchange.

Just did this now - I don't know what it's supposed to be, but I get ~2V
DC. What does that mean?


It's supposed to be about 42 volts. Does your ADSL work perfectly ?

If so it probably isn't the line at all but a dodgy board or connector at
the telephone equipment at their end. The signal comes out of this and then
into the ADSL rack then out to you. This really is "spagetti junction"
with huge bundles of 50 pairs dangling all over the place and a single
damaged or intermittent wire wouldn't surprise me.

You can get VoIP as a backup. This uses the ADSL for voice and whilst you
would aquire another phone number it would give you some form of service.

Mike wrote:

It's supposed to be about 42 volts. Does your ADSL work perfectly ?

It's now on/off, but when it's on, I can get about 960Mbit.


If so it probably isn't the line at all but a dodgy board or connector at
the telephone equipment at their end. The signal comes out of this and then
into the ADSL rack then out to you. This really is "spagetti junction"
with huge bundles of 50 pairs dangling all over the place and a single
damaged or intermittent wire wouldn't surprise me.

You can get VoIP as a backup. This uses the ADSL for voice and whilst you
would aquire another phone number it would give you some form of service.

Yes, we use voip between our offices, and i have a couple of voip-pots
accounts.



--
Grunff

Andy Hall wrote:

There should be about 50v DC so it means that one or both legs of the
line are class F.


Amazing it still works then!


--
Grunff

Grunff wrote:
Andy Hall wrote:

There should be about 50v DC so it means that one or both legs of the
line are class F.



Amazing it still works then!


We had the same problem a couple of months ago - ADSL worked fine (I
didn't actually check data rates but there was no slowdown evident) but
there was no voice service. The phone would ring on incoming calls, but
no connection and no dial tone. Not sure if the GF was more annoyed at
the loss of the voice service or the lack of loss of the ADSL service :-)

Cheers,

Chris

--
cut along the dotted line to reply

In article , Grunff
writes

As in my reply to Dave L, it just doesn't help. They are totally
useless, and don't know the meaning of customer service.

Standard advice in uk.telecom in situations of this sort is to contact
Ben Verwaayen's office by email. A google groups search will get you
the address.

--
..sigmonster on vacation

Grunff wrote:

It's now on/off, but when it's on, I can get about 960Mbit.

Now that is the sort of broadband I would like - just under a Tbit all
to myself ;-)

(I spose you mean 960kbit... oh well)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:

It's now on/off, but when it's on, I can get about 960Mbit.


Now that is the sort of broadband I would like - just under a Tbit all
to myself ;-)

(I spose you mean 960kbit... oh well)

D'oh!!


--
Grunff

On Sun, 19 Dec 2004 08:30:49 +0000, Grunff wrote:

Lat time we had 2x ISDN (two separate pairs) lines down for 11 days.
I think it was about =A3300 compensation. I can't even begin to
calculate the cost to us :-(

ISTR something about being able to claim actual losses, if you can
reasonably prove those losses...

2v on the line, with nothing off hook, is wrong it should be around
50v.

--
Cheers
Dave. pam is missing e-mail

Mike Tomlinson wrote:

Standard advice in uk.telecom in situations of this sort is to contact
Ben Verwaayen's office by email. A google groups search will get you
the address.


Does that actually achieve anything? I receive many, many apologies,
from a whole bunch of different people at BT - but they are totally
meaningless unless backed by some action.


--
Grunff

"Grunff" wrote in message
...
Mike Tomlinson wrote:

Standard advice in uk.telecom in situations of this sort is to contact
Ben Verwaayen's office by email. A google groups search will get you
the address.


Does that actually achieve anything? I receive many, many apologies, from
a whole bunch of different people at BT - but they are totally meaningless
unless backed by some action.

The trick is to make fixing your problem less hassle than having you keep
rattling cages. I rarely go 'up the chain of command' more than one step
before 'phoning head office and asking for the MD.

On one occassion I contacted the US main office of a 'white goods' maker as
it was after hours in the UK. European MD rang me that evening (from Italy)
and appliance was fixed the next day, at a time convenient to me. I also got
a free extended warranty on the fridge until I had a fault free year!

Brian

Dave Liquorice wrote:

ISTR something about being able to claim actual losses, if you can
reasonably prove those losses...

Difficult - the reason we have so many lines is because we really can't
afford to have any downtime - so the worst it's been so far is down to
one single line, but even that's good enough for two of us to work off.
So no 'losses' apart from the many hours spent on the phone to BT (now
that probably comes to several thousand pounds; but that's a different
story).


2v on the line, with nothing off hook, is wrong it should be around
50v.

Yeah, that was at the master socket with everything disconnected.


--
Grunff

In article ,
Brian Reay wrote:
The trick is to make fixing your problem less hassle than having you
keep rattling cages. I rarely go 'up the chain of command' more than
one step before 'phoning head office and asking for the MD.

After Parcel Force lost a computer I'd sent to my brother, they pulled
every single delaying trick in the book to avoid paying up. One letter
direct to the MD got a full settlement of my claim instantly.

--
*Virtual reality is its own reward *

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Grunff
writes
Mike Tomlinson wrote:

Standard advice in uk.telecom in situations of this sort is to contact
Ben Verwaayen's office by email. A google groups search will get you
the address.


Does that actually achieve anything? I receive many, many apologies,
from a whole bunch of different people at BT - but they are totally
meaningless unless backed by some action.

According to several posters in uk.telecom, yes. I wouldn't have
suggested it otherwise.

--
..sigmonster on vacation

Mike Tomlinson wrote:

According to several posters in uk.telecom, yes. I wouldn't have
suggested it otherwise.

Great! I wasn't questioning your suggestion - it sounds reasonable
enough - I was just asking whether you knew how effective it might be. I
think I'll deffinitely give it a try, thanks.



--
Grunff

Grunff wrote:

Dave Plowman (News) wrote:

Have you checked for DC on the incoming line? That would show if it's
intact to the exchange.


Just did this now - I don't know what it's supposed to be, but I get ~2V
DC. What does that mean?

Its shagged.
Should be about 90V.
At about 10mA short circuit IIRC.

It may be that its disconnected from the baseband kit at the far end.

On Sun, 19 Dec 2004 21:11:26 +0000, The Natural Philosopher
wrote:

Grunff wrote:

Dave Plowman (News) wrote:

Have you checked for DC on the incoming line? That would show if it's
intact to the exchange.


Just did this now - I don't know what it's supposed to be, but I get ~2V
DC. What does that mean?

Its shagged.
Should be about 90V.

Nominally 50V.

The ringing voltage is somewhere around 90V at a frequency of 25Hz.

Frank Erskine
MJBC, OETKBC

Lurch wrote:

ADSL is carried at a radio frequency (RF) so will effectively 'jump'
gaps in cables.

At the very low radio frequencies used by ADSL (~30 - ~500 kHz, AIUI)
the signal attenuation involved in 'jumping the gap' in a broken wire
will be huge[1]. What's far more likely to be happening is that the
stray capacitance of the o/c wire (on the subscriber's side of the
break) to earth, or, more particularly, to all the other pairs in a
multi-pair cable, is providing a 'return' connection.

For an electrical current to flow you are quite correct though.

Well someone needs to point out that a one-wire connection still depends
on the flow of electric current ;-) How do you think aerials work?


[1] The ADSL modem in my roota usually claims an SNR margin of around 30
dB, so clearly there is a lot of margin in the system. Capacitive
coupling across the gap in a broken wire at these frequencies though is
going to introduce probably 60+ dB of attenuation - so that isn't the
answer...

--
Andy

"Andy Wade" wrote in message
...

[1] The ADSL modem in my roota usually claims an SNR margin of around 30
dB, so clearly there is a lot of margin in the system.

Getting up to 8Mbps through the system with 30dB noise margin took years of
design effort and years arguing in standards forums about what the best
method was. If you think of it another way, with 0dB margin it is
difficult to get much through at all.

Frank Erskine wrote:

On Sun, 19 Dec 2004 21:11:26 +0000, The Natural Philosopher
wrote:


Grunff wrote:


Dave Plowman (News) wrote:


Have you checked for DC on the incoming line? That would show if it's
intact to the exchange.


Just did this now - I don't know what it's supposed to be, but I get ~2V
DC. What does that mean?


Its shagged.
Should be about 90V.


Nominally 50V.

The ringing voltage is somewhere around 90V at a frequency of 25Hz.

Right. Its been some time...you R right and I was wrong.


Frank Erskine
MJBC, OETKBC

The Natural Philosopher wrote:

Its shagged.
Should be about 90V.



Nominally 50V.

The ringing voltage is somewhere around 90V at a frequency of 25Hz.


Right. Its been some time...you R right and I was wrong.


ISDN lines should be 90-100V.


--
Grunff

In article ,
The Natural Philosopher wrote:
The ringing voltage is somewhere around 90V at a frequency of 25Hz.

Right. Its been some time...you R right and I was wrong.

Funny. I had 17 Hz in my mind. Wonder where that came from?

--
*And don't start a sentence with a conjunction *

Dave Plowman London SW
To e-mail, change noise into sound.

On Tue, 21 Dec 2004 01:19:34 +0000, Grunff wrote:

ISDN lines should be 90-100V.

But this must be a POTS line as ADSL can't co-habit with ISDN
(according to BT).

--
Cheers
Dave. pam is missing e-mail

On Tue, 21 Dec 2004 01:32:53 +0000 (GMT), Dave Plowman (News) wrote:

Funny. I had 17 Hz in my mind. Wonder where that came from?

Donno, but ringing frequency varies greatly around the world, quick
dig on the net gave 17Hz to 68hz... However the BT SIN says 25Hz +1Hz
-5Hz:

http://www1.btwebworld.com/sinet/351v4p1.pdf

--
Cheers
Dave. pam is missing e-mail