[Gllug] ADSL problem

[Christopher Hunter]

On Friday 25 Feb 2005 11:40, will wrote:
> t.clarke wrote:
> > Is the only socket in use the first physical/primary socket in the house
> > ? (ie first one in the 'chain' from where the line comes into the house)
>
> I suspect so, it is the only one downstairs, but I will have to check.
>
> > If so, suggest you try and physically disconnect all the other sockets
> > from it so you have only the following layout:-
> >
> >        bt line              |----| |-----|-----PHONE
> > ============================| A  |=| B   |
> >
> >                             |----| |-----|-----ROUTER
> >
> > A=socket;  B=Microfilter
> >
> >
> > If the problem persists the I presume the problem is with the
> > microfilter.
>
> I have a new one to test, but I suspect that the problem could be
> something else, other microfilters have the same problem.
>
> > Normally 'ringing' is supplied from the exchange as 50V (or thereabouts)
> > AC with enough juice (a) to give you a jolt if you touch the wires and
> > (b) to drive the ringer on one of the older phones.  I believe the modern
> > phones using electronic ring tones do not use the AC to drive the ringing
> > directly but merely detect it and then generate the ringing internally. 
> > Thus, spurious AC of any sort on the line, I believe, can cause the phone
> > to ring.
>
> Thanks for the advice (and Thanks to Chris Bell in his other post).
>
> Will.

It's almost certainly a wiring error in your telephone socket wiring somewhere 
in the house, possibly a reversal of the line pair.

If you examine the insides of the telephone sockets there are only three of 
the six terminals that are of importance - numbers 2, 3, and 5.  The external 
line should come into the first socket on terminals 2 and 5.  There is a 
capacitor inside the first socket (called the "master" socket in BT parlance) 
which feeds the AC ringing signal to terminal 3.  All the extension sockets 
are wired in parallel - 2 to 2, 3 to 3, and 5 to 5, and the extensions lack 
the capacitor.  The wiring scheme is really simple (it has to be for the 
average BT employee) - just make sure that the colour coding from the master 
to all the slave sockets is consistent.

If you have a multimeter, you should find roughly 48 V DC across terminals 2 
and 5 at every socket, and the polarity MUST be the same in every case.  If 
you take a phone off the hook, a good line will show a DC voltage of 8 to 10 
V.  Ringing is normally 80 V AC at either 18 or 25 Hz (depends on the 
exchange), so mind your fingers if you're expecting a call!

Chris
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