The HP Model 8555A Spectrum Analyzer RF Section is shown in Figure 1-1 with the Model 8552B Spectrum Analyzer IF Section and the Model 141T Display Section. Table 1-1, Specifications, and Table 1-2, Supplemental Performance Characteristics, are for the 8555A RF Section when used with an 8552A/B IF Section and a 140-series Display Section. The 8555A plug-in is the microwave RF Section for use with the 8552-series IF section and the 140-series display section. Together they comprise a receiver that electronically scans an input signal and provides a visual display in the frequency domain. Input signal amplitude is plotted on the CRT as a function of frequency. The amplitude (Y-axis) of the CRT is calibrated in absolute units of power (dBm) or voltage (juV/mV) (50-ohm system): accordingly, absolute and relative measurements of both amplitude and frequency can be made.