What indicates that the Doppler navigation system is in memory mode?

The indication that the Doppler navigation system is in memory mode is represented by the appearance of an "M" in a cut-out window on the indicator. This "M" serves as a visual cue to the operator, signaling that the system has stored certain data or parameters, allowing for navigational reference without continuous input or adjustment from the user.

In contrast, while a sound alert can indicate various statuses or conditions within the system, it does not specifically denote memory mode. A change in beam angle relates to the operational adjustments of the radar system but is not a direct indicator of the memory mode. Similarly, screen flashing could suggest different types of alerts or indicators, but it does not specifically correlate to the memory function.