Hence why I asked the OP to try a phone, and establish if it's the fax or the line itself.

sorry did not make it to the premises today to experiment.
thank you for your interest.
i understand that the A /B terminals are for the BT drop only.
and this is the way it is wired.
the output from the bt master is from 2 and 5 and i have used the punching handtool to effect this.
the master and slaves are wired correctly but i have been doing sparky work for so long that i am not up to speed on filters and got careless on this job.
i mentioned the A/B original wiring as i vaguely think this was how it was wired before i took it apart.
the catalogue of faults was intermittant broadband logon
and on saturday the fax stopped working.
on testing the fax it would fax once and afterwards gave comms error.
went over my installation and found that i had carelessly made 3 mistakes
1 installed a master as the first slave which i rectified
2 mixed up the wiring so that the 2 slaves had a cross connection between 2 and 5
which i rectified
3 had connected the output of the bt master from A B terminals to the slaves which i rectified. ie parralled the drop wires and slave wires. now rectified.
by this time i got a second fax machine installed (have not reinstalled the original fax)
so broadband connected to first slave and also i connected a phone in parralel when it said no dialing tone - there was and 48 volts dc.
the second slave has the card machine and the fax together.
both work correctly.
but
the broadband logon says failure no dialling tone, (there is ), but logs on when i disconnect the fax almost automatically.
i now think that the answer will be filtering but will not know till monday
will also try a phone in place of fax to see result cheers
sorry for the long winded explanation
cheers

sorry for the confusion of the bt master socket
just to clarify
the bt master is in 3 parts where you align the test socket and push home ( 2 short screws) against a plate with 2 longer screws
bt input to screw terminals A and B ( nothing on associated earth screw terminal)
test socket on front - nothing connected.
the output to first slave i have connected to i believe its the inside of the faceplate
it is two rows of 3 connections ( same connections as on most modern master and slaves where you use the tool to punch in the wires) with numbers 1 to 6 and i am using 2 and 5
cheers

If there is nothing connected to the test socket - the wire must be connected to the back of the master plate adjacent to the A&B terminals.

Your connections should be made to the removable part of the face plate - the very front and this then connects into the test socket.

Hi, reading your problem and noticed this:
"2nd slave has a bankcard swipe card on a normal tel plug and a rj11 feeding a fax "

RJ11 feeding fax...
Is that RJ11 both ends of lead, or an RJ11 at one end and BT jack at the other end.

If it's the 1st type (RJ11 to RJ11) would this not force you into plugging your fax incorrectly into the DSL port on your filter?

Only reason I ask is that this is a very common mistake with many (especially new) phones and faxes as manufacturers seem to favour providing an RJ11 to RJ11 lead + RJ11 to BT adapter, which many folk ignore or lose!!!

yes the fax is rj11 to rj11
i have the slave (last on line)
a spitter plugged into the slave
this splitter has normal socket to accept phone ect this is used for swipe card
and an rj11 socket to accept fax
the swipecard has internal test facility regarding line voltage and ren loading
this tests ok and works ok
i have no filter plugged in as yet
i also changed the slave socket, the splitter and the rj11 lead
but the broadband ( has a filter) on the other slave will only logon when the fax is disconnected
i am now assuming that the fax not having a filter is the problem
or maybe part of it but did not fully understand the last poster regarding a common mistake cheers

In reply to a post by clydey:

i am now assuming that the fax not having a filter is the problem

Nor does the swipe card have a filter when it should = another part of same problem. You need a filter plugged str8 in the slave socket before the splitter and it will cover both. Sometimes you my need 2 filters in series.

BTW: BB does not have filters; phones do.

thank you for this information
i will put a filter into the slave before the splitter as said
many thanks