The 37XXXD Network Analyzer is a single-instrument system that contains a built-in source, test set, and analyzer. It is produced in two series— 372XXD and 373XXD. All models provide up to 1601 measurement data points, a built-in hard-disk drive for storing and recalling front panel setups and measurement and calibration data. They also provide an on-screen display of total operational time and dates of system calibrations. They support operation over the IEEE 488.2 General Purpose Interface Bus (GPIB).