When you are using an ISDN adapter and Dial-Up Networking, you may encounter error messages stating that the "modem" is not responding or the "modem" is not configured properly. These messages are incorrect, because an ISDN adapter is not actually a modem (modulator/demodulator). An ISDN adapter uses an all-digital signal and does not need to modulate or demodulate the signal.

This behavior occurs because the Dial-Up Networking tool was not written with ISDN devices in mind. Therefore, error messages make references to a "modem" instead of the ISDN device.