What is a graticule in the context of a CRT?

A graticule in the context of a CRT (Cathode Ray Tube) refers to a calibrated scale that is used to provide a visual reference for measuring the amplitude of signals over time. It typically appears as a grid or set of lines on the phosphor screen of the CRT, allowing for precise readings of waveforms during oscilloscopes or other display applications. This calibrated scale helps users to analyze the waveform characteristics, such as frequency, amplitude, and timing, facilitating effective measurement and troubleshooting in electronic environments.

By using the graticule, technicians and engineers can visually interpret and quantify the parameters of the signals being studied, making it an essential feature in signal analysis. The other options do not accurately describe the role of a graticule: adjusting focus relates to picture clarity, brightness control manages the intensity of the display, and amplification pertains to increasing the power of signals, none of which aligns with the function of a graticule.