The HP 8472A Crystal Detector is a 50 Ohm (nominal) device designed for measurement use in coaxial systems. The instrument converts RF power levels applied to the 50 Ohm input connector into proportional values of dc voltage.  The instrument measures relative power up to 100 mW and has a BNC female connector for the output jack which allows the detected output to be connected to a SWR meter.  The output voltage polarity is negative, unless Option 003 is selected.  The frequency range of the 8472A is 10 MHz to 18 GHz.