For Windows Mobile you can find a very detailed description of the required settings in both our Software Manual and our WANGPRS Library Manual.
If you want to use telephony functions, you can either work with Microsoft TAPI or OpenNETCF Telephony Library for the Compact Framework.
Power Management (Windows Mobile)
If there is no SIM card inserted or the signal strength of the phone is low, CPU speed is switched to "POWER SAVING" automatically. While CPU power is down, the device might respond slowly. In such a scenario you should consider disabling the power management for the phone by creating a new value in the registry (see below) and/or deleting the shortcut "log.lnk" at \Windows\StartUp. Additionally, you should increase the CPU speed at START, SETTINGS, SYSTEM, CPU SPEED. e.g. to "TURBO". After changing the registry, perform a soft reset operation to reboot the device with the new settings.
Phone Power Management: [HKEY_LOCAL_MACHINE\Software\Casio\RssiCpuSpeed]
Disables automatic POWER SAVING mode
Enables automatic POWER SAVING mode (default)