Modems differ in their use of the Hayes command set. The PCMCIA Expansion Module and PowerBook 5300/1400 allow you to plug in a modem, but operating the modem and setting up your software to use the modem and connect to other services is not within the control of the PCMCIA hardware and software. You need to consult the user guide and/or the tech support service of your modem manufacturer and your modem software publisher to determine the correct AT commands.
To determine whether or not the modem is being made available (which is all that Apple’s software is responsible for), get into the setup connection dialog. Its exact name and location varies from program to program. The method or tool (again, terms vary) should usually be Serial Tool. In some cases, Apple Modem Tool will also work.
When Serial Tool is selected, a window containing choices for port should appear. This window might have a horizontal scroll bar. The window will likely contain icons named, for example, modem/printer and upper card slot. If either upper card slot or lower card slot appears, then the PowerBook is working correctly (If the window also contains internal modem, then you have a built-in internal modem. This is not the same as your PCMCIA modem.) You should click the upper card slot (or lower card slot) icon to select the PCMCIA modem.
Further modem configuration, such as speed, handshaking, setup strings, AT commands, and so on, are the responsibility of the user, and the modem and software provider. Those settings should not be affected by whether the user has a modem plugged into the PCMCIA slot or an external modem plugged into the back of the computer. The PCMCIA Expansion Module and the 5300/1400 makes the modem available, but it does not control it.