The Model 560A Scalar Network Analyzer is a GPIB-compatible, three-channel microwave measurement instrument. The three channels consist of two measurement channels (A, B) and one reference channel (R), which allow the network analyzer to simultaneously display the results of two measurements. The 560A also contains internal memory circuits that provide two different functions — measurement-normalization memory and display-refresh memory. The measurement-normalization memory stores transmission measurement system residuals and return loss calibration data. The display-refresh memory provides a non-flickering display, regardless of sweep generator sweep speed. The refresh memory also provides for a slow, 30-second sweep for an external X-Y plotter.