Hi All,

I am trying to interface a pulse transformer to a logic circuit (FPGA) but I am not sure what would be the optimal circuit to detect the pulses including polarity. The incoming signal is coded as "1" - no signal, "0" - 5.2 usec pulses of alternating polarity. I could find some circuits and ideas but not dealing with the polarity problem.

It just started as a curiosity idea - I still have the rare thing at home: an ISDN phone line and I am wondering if I can monitor the signal on the line (the 4-wire S interface, not the 2-wire U interface which would be much more difficult). I have got the ISDN pulse transformer T5012-NL from Mouser and experimenting with it (an oscilloscope would be very useful I guess but I have only 34-channel logic analyzer as I work with digital circuits most of the time ...)

I have read the ITU recommendation I.430 which describes the line code in detail but does not help me with the pulse transformer problem unfortunately.

Thanks for any help.

Petr