Some types of probe changers have a serial connection to the computer. Use the Comm tab in the Probe Changer dialog box (Edit | Preferences | Probe Changer) to choose your communications port (COM port) and modify your COM port settings. For information on your COM port settings, check the documentation that came with your computer hardware.
Probe Changer dialog box - Comm tab
The Comm tab does appear if your probe changer does not have a serial connection.