The Keysight / Agilent / HP 853A Spectrum Analyzer Display is a digital display mainframe for use with the 8557A, 8558B, and 8559A Spectrum Analyzer Plug-Ins. Signals are displayed on either of two independently stored digital traces. Display processing capabilities include maximum hold, digital averaging, and trace normalization. A built-in microprocessor manages the display operation and provides access (via the front-panel) to built-in test routines for display calibration and testing. Direct plotter control.