Agilent Technologies ESA Series User's/Programmer's Reference page 335

Signal identification is not available with signal track, resolution bandwidths ≤ 300
NOTE
Hz, demod, or averaging. Signal identification will be turned off when input mixer
is set to internal.
Front Panel
Access:
Chapter 5
To synchronize in image shift mode, turn off signal
identification, initiate a single sweep, and turn on signal
identification. The results of the first sweep after signal
identification is turned on must be ignored. The data from the
second sweep is available in Trace 1 and the data from the third
(shifted) sweep is available in Trace 2.
Input/Output (or Input), Input Mixer, Signal Ident On Off
Remote Command Reference
[:SENSe]:SIDentify Subsection
335