What type of signals does the RSDS warn aircrew about?

The correct answer is radar signals. Radar signals are specifically used in various systems to detect and track aircraft and other objects in the surrounding environment. The Radar System Detection System (RSDS) is designed to provide aircrews with warnings about potential threats, typically focusing on the presence of radar systems that could pose a danger to flight operations.

Radar signals are crucial for aircrew to understand their operational environment, as they can indicate the presence of enemy radars or tracking systems that may be targeting them. This enhances the situational awareness of the pilots and enables them to take necessary evasive actions or countermeasures.

While audio, laser, and infrared signals play roles in different detection and warning systems, they do not specifically pertain to the RSDS's primary function of monitoring radar signals, which is why they are not the correct answer in this context.