[Gllug] [OT] Testing internal line quality

[Chris Bell]

On Fri 14 Oct, Simon Perry wrote:
> 
> James Goldwater wrote:
> > I have a colleague/client who is having persistent trouble connecting to
> > the internet via ADSL: it often requires numerous attempts to log on,
> > and the connection is sometimes dropped.
> 
> There are several reasons that this may be happening only a small subset
> will be down to line quality or internal wiring. Are you sure that it is
> synchronisation with the dslam that is being lost? If that is so is that
> a known issue with the routers that you are using?
> 
> > AFAIK, BT insist that the line is good enough, therefore the problem may
> > be in the house wiring.  Routers have been swapped out to no effect.
> > Alledgedly the line goes straight into the home office, so there are no
> > extra sockets and microfilter issues.
> 
> I'm having a running battle with BT at the moment with the home phone
> where they claim all is ok but the ADSL is down more than up and even
> the phone is unusable most of the time!
> > 
> > So as a quickie starter for ten, how can I measure internal line
> > quality?  Is there a meaningful metric?
> 

   If it is a line dedicated to ADSL then, as Jason says, you do not need to
use a microfilter except as a plug adaptor, but it is not a good idea to
assume that it does not have a fault.
   Plug a phone into the vacant socket and listen for line noise, it should
be quiet. If you get dial tone just dial one digit.
   If you have the type of BT box with a removable lower half front, try
using the socket behind.
   Common problems are caused by water, or trees brushing against overhead
lines. BT should have ripped out all the aluminium wire by now, otherwise
the line volts rapidly make cable joints go high resistance. BT standard
tests should soon find a standard cable fault, but if you say that another
line is noisy there may be a short between adjacent wire pairs, and some of
the ADSL is being lost. Does an ADSL filter affect the audible noise on the
other line?
   If you are a long way from the exchange, so the line is marginal, and you
have the type of BT box with a removable lower half front, then the full BT
spec replacement front panel with integral filter is by far the best. They
are more expensive than the normal external filters, but you only need one.
The telephone ringer circuit causes problems with the filter design, so it
is moved from the exchange side to the phone side of the filter.

-- 
Chris Bell

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