My thought is that if a dialup modem will work with either a BT or a NTL line, without any changes, then NTL lines are PSTN compatible.
- I have also used a portable (non dect) cordless phone with both a BT & a NTL line with no problems. Our current dect one works fine on our NTL line, as does a normal wired one.
<edit> thanks for the confirmation, Bill