Another filter question- no really a new one

A friend is having problems with a home made extension lead from a filter to
the PC.

He has a standard bt socket on one end, an RJ45 on the other into the
filter.

A telephone handset gets no signal when plugged into the extension, although
many posts in this group have said the modem side of the filter is a
straight through connection.

He also has tried three different bt socket to RJ45 adapters to connect the
modem to the socket, one of these has four pins connected, the others only
have two pins. the middle two pins of the RJ45 socket are connected to the
outer two pins of the middle four of the BT socket.

The modem only works when using the four pin version, and the telephone
handset will work if one of these adapters is used instead of the filter at
the other end.

Can anyone explain how the BT to RJ45 connection should work, and why no
telephone signal on the modem side of the filter? Is this side filtered too?
And why does it need four wires connected, when all the books say only two
are needed?







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On Fri, 23 Jan 2004 16:46:56 -0000, "Nat Stott"
<(E-Mail Removed)> wrote:

>He has a standard bt socket on one end, an RJ45 on the other into the
>filter.

why ? did the modem have a BT plug or something.

>A telephone handset gets no signal when plugged into the extension, although
>many posts in this group have said the modem side of the filter is a
>straight through connection.

it is an unfiltered connection, it is not "straight through" in the
sense that 2&5 on the BT plug are connected to 3&4 on the RJ11 / RJ45
socket http://www.adslnation.com/support/filters.php

>
>The modem only works when using the four pin version, and the telephone
>handset will work if one of these adapters is used instead of the filter at
>the other end.

sounds like the adaptor is correcting a wiring error in the extension.
The 4 pin version of the adaptor must be connecting the pins with the
signal to the modem pins needing it.

Some modems that ship with a BT lead might have the input on 2&5 so
that a straight through cable (IDC connectors) gives the right
connection with an RJ11 plug on one end and a BT plug on the other.

On a similar basis some adaptors supplied with modems do funny things.
The only way to be sure is to examine the orginal lead, or the modem
manual, to see what it is expecting. Then determine if the adaptors
are pin for pin or crossover and check the leads. Draw it all on a bit
of paper and all will become clear. A condictivity tester would be
useful :-)

Phil

> >The modem only works when using the four pin version, and the telephone
> >handset will work if one of these adapters is used instead of the filter
at
> >the other end.
>
> sounds like the adaptor is correcting a wiring error in the extension.
> The 4 pin version of the adaptor must be connecting the pins with the
> signal to the modem pins needing it.

Thats what I thought too, but as he wired it himself I couldn't convince
him.

> Some modems that ship with a BT lead might have the input on 2&5 so
> that a straight through cable (IDC connectors) gives the right
> connection with an RJ11 plug on one end and a BT plug on the other.
>
> On a similar basis some adaptors supplied with modems do funny things.
> The only way to be sure is to examine the orginal lead, or the modem
> manual, to see what it is expecting. Then determine if the adaptors
> are pin for pin or crossover and check the leads. Draw it all on a bit
> of paper and all will become clear. A condictivity tester would be
> useful :-)
>
> Phil

Didn't have any testers when I popped round there at lunchtime. Need to have
another look.

Thanks for the link.



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