Agilent Technologies Infiniium 8000A Programmer's Reference Manual page 210

Query
Returned Format
Example
Channel Commands
PROBe:EXTernal:GAIN
:CHANnel<N>:PROBe:EXTernal:GAIN?
The :CHANnel<N>:PROBe:EXTernal:GAIN? query returns the probe external
gain setting for the selected channel.
[:CHANnel<N>:PROBe:EXTernal:GAIN]
This example places the external gain value of the probe on the specified
channel in the variable, Gain, then prints the contents of the variable to the
computer's screen.
10 OUTPUT 707;":CHANNEL1:PROBE:EXTERNAL ON"
20 OUTPUT 707;":CHANNEL1:PROBE:EXTERNAL:GAIN?"
30 ENTER 707;Gain
40 PRINT Gain
50 END
10-16
<gain_factor>
<NL>