Agilent Technologies 8719D User Manual page 354

The TRL/LRM two-port calibration, activated by pressing the ~~~~:~~~~~T softkey within
the calibrate menu, provides the ability to make calibrations using the TRL or LRM method.
True TRL/LRM calibration is available on instruments equipped with Option 400, Four Sampler
Test Set. For more information, refer to "TRL/LRM Calibration," located later in this section.