What indicates that a radar unit is functioning correctly during pre-use checks?

A consistent test reading is a crucial indicator that a radar unit is functioning correctly during pre-use checks. This test reading is typically established using a tuning fork or similar device that provides a known speed, allowing the operator to verify that the radar unit accurately detects and displays that speed. If the radar consistently reflects this known speed, it demonstrates that the internal components and calibration of the unit are operating properly.

Other options may relate to the overall operation of the radar unit but do not specifically confirm correct functioning during pre-use checks. For instance, while having no noise during operation is desirable, it does not directly verify the accuracy of the speed readings. Showing the maximum speed limit could be a function of the radar unit, but it is not essential for verifying the operational status. Additionally, an officer's visual estimation, while valuable, is subjective and can vary; it does not provide a standardized measure of the radar's performance. Therefore, a consistent test reading is the most reliable indication of correct functioning.