Which of the following describes a characteristic of secondary radar?

Answer: B — It requires aircraft transponder signals to function

Secondary radar is characterized by its reliance on aircraft transponder signals to function effectively. This system operates by sending out an interrogation signal from the ground station, which prompts an aircraft's transponder to respond with its unique identification information and additional data, such as altitude. This interaction allows secondary radar to provide more precise information about the aircraft than primary radar, which only detects the radar signal reflected off the aircraft itself. The requirement for transponder signals is a fundamental aspect of secondary radar, making it dependent on aircraft cooperation for optimal operation. Additionally, this cooperation enhances the accuracy and detail of the information presented to air traffic controllers, contributing to safer and more efficient air traffic management. In contrast, the other options do not accurately reflect the characteristics of secondary radar. For instance, secondary radar cannot operate independently as it specifically relies on the transponder responses from aircraft, and it is not limited to ground-based radar stations only; it involves both ground and aircraft equipment. Furthermore, while secondary radar does provide visual information on radar screens, it does not typically generate imagery in the same way as primary radar but rather presents data in a format that helps controllers track and identify aircraft.