What must be pressed along with the CAL/AF switch to display the message "NUC in progress"?

To display the message "NUC in progress," the Menu Switch must be pressed alongside the CAL/AF switch. The juxtaposition of these two switches is significant because the Menu Switch often serves to navigate through different operational modes or display options on marine electronic devices. When performing certain tasks, like initiating a Network Update Condition (NUC) procedure, it's essential to access the appropriate menu settings to confirm that the process is underway.

Other switches like the Power Switch, Mode Switch, and Control Switch have separate functions, such as powering the device on or off, switching operational modes, or adjusting settings. They do not play a role in specifically accessing the menu required to display the NUC message. Hence, only the combination of the CAL/AF switch and the Menu Switch successfully brings up the desired display.