TDM400 in the UK

I have a TDM400 with 2 FXO & 2 FXS. One incoming FXO line is from an existing PBX extension and works fine. The other is from BT and behaves totally erratically. * hears ringing, answers it, drops it, answers it again, drops it again continuously. CLI is read one time in five.

I have tried almost every variation of CLI polarity, answeronpolarity, droponpolarity etc.

Does anyone have any idea what is going on? Normal phone plugged into socket works fine. The only thing that might be unusual is that I had to re-do all the house phone wiring to get an extension near the * box and I now only have one extension on the line rather that about six. Do you need some sort of special master socket on a BT line?

And does anyone have a simple zap conf file that actually works reliably in the UK?

sounds like it has to do either with call progress detection or gain settings (maybe both). Make sure the gain is set right on the zap port, and try turning off call progress detection.


UK bt lines must have a master socket on it as the master socket has the resistor and capacitor for the ringing circuit. You can have the tdm in a normal socket as long as somewhere on the phone line you have the master socket.