What_does - I have no desire to get into a war of words here or pee you off as moderator of this forum.
However, I have been in this game too long. You mention a PSTN adapter ? I assume you mean a software PSTN adapter ? When I use ISDN my PC network talks ISDN from the card via the ISDN line. All calls within the network, be it our friends at BT or whoever, talk ISDN (albeit on a larger scale) until the final stretch from the destination exchange. I.e. it is pure ISDN from within my PC to the destination so no need for conversion. Analogue only comes into play at the last part of the call. That is totally
transparent.
I apologise if I am treading on toes here. Suspect I have mis-read and that the original post was more related to conguration of the TA itself.