What components are typically checked when testing RADAR?

The correct choice highlights critical components that ensure the RADAR system operates effectively. When testing a RADAR unit, checking the lights, display, and internal circuits is vital because these elements are essential for proper functionality. The lights confirm that the machine is powered on and operational, while the display provides essential visual feedback on the observed speed and operational status. Additionally, examining the internal circuits is crucial to ensure that the electronic components are functioning correctly, as they manage data processing and communication within the RADAR unit.

Other options, while possibly relevant in a broader context, do not focus as directly on the core components necessary for assessing RADAR functionality. For instance, audio tone and speed settings can be important but are secondary to ensuring that the foundational elements of the RADAR system — like its lights and display — are working correctly. Similarly, frequency and alignment are relevant to RADAR performance but are not components that would typically be visually inspected during routine checks. Thus, the focus on lights, display, and internal circuits makes the selected answer the most accurate in the context of routine RADAR testing.