HP 81101A Reference Manual page 55

Command
:FREQ:AUTO
Long
[:SOURce]:FREQuency[:CW|:FIXed]:AUTO
Form
Event
Parameter
ONCE
*RST value
Not applicable
Description
Use this command to measure the frequency at the CLK-IN connector. If
the CLK-IN connector is the selected pulse frequency source, you can
then read the measured value with :FREQ?
Example
To measure and read the frequency at the CLK-IN connector:
:TRIG:SOUR EXT
:FREQ:AUTO ONCE
:FREQ?
Command
:HOLD
Long
[:SOURce]:HOLD
Form
Set & Query
Parameter
VOLTage | CURRent
*RST value
VOLT
Description
Use this command to enable either of the [:SOURce]:VOLTage or
[:SOURce]:CURRent subsystems.
You can control the signal levels of the instrument's OUTPUT in terms of
voltage or current.
Programming Reference
SCPI Instrument Command List
Select ext CLK-IN as pulse trigger
Measure frequency at CLK-IN
Query pulse frequency
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