Our PowerBooks with Express Modems are not able to dial into our network using White Knight because of a problem with our TrackNet device and the Express Modem script. TrackNet is a security device used for dial-back and works fine with everything except Express Modems in PowerBooks.
In order to make connection using other modems, or another CPU with an external modem, the command ATDT* must be entered a few milliseconds after the dial-back ring is detected by the initiating CPU. When the ATDT* command is issued, the Express Modem returns "MODEM IN USE," however, other modems do not do this.
Type ATH1DT* instead of ATDT* to avoid the 6 second timeout. The H1 command forces the modem to go off hook which then allows the dial command to proceed.