I now have the filter you recomended, Standard connection seems very straightforward (2,5 from BT Master to 2,5 on filter,

then F2, F5 to Panel).

But for line seizure (as required by EN50131) Do I need to connect another secondary socket to the master and connect devices to that which were previously connected to the Master? Ensuring nothing is plugged into the master.

as monty, can be wired for line seize, but really needed.

fitted loads with no issue, could be down to no filter fitted.

have the correct line fault programming been done, think its volts and low security for shared line.

If the line fault programming is set to Line + volts (as default) on a shared line can it cause non function of phone line when panel goes into line fault state?

i.e now when anyone dials the line, it only goes straight to fax, and there mad interference on the phone, seems if the panel messed up the line when going into line fault.

just wanted to be prepared for worst scenario when I go to reprogram correct line fault.

if its speech dialler, then it doesnt need line seize for the regs