Agilent Technologies ESA Series User's/Programmer's Reference page 106

Front-Panel Key Reference
Input/Output
Mixer Bias
On Off
106
activates and allows
(On)
Mixer Bias
adjustment of an internal bias source
for use with external mixers. The bias
signal is present on the center
conductor of the IF INPUT connector
on the front panel. The mixer bias will
be if
Off Harmonic (Auto)
is selected.
Mixer Type (Presel)
Key Access:
Input/Output
Mixer Config
and
, ,
Input Mixer
Chapter 2