Keysight Technologies N9321C User Manual page 170

Key Reference
Sweep
162
Gated View
When Gate View is set to off, the display is in frequency domain.
When Gate View is set to On, the display is in time domain (zero
span), the gate length is shown in red lines for further adjustment.
View SweepTime
Adjust the sweep time scale to set the gate parameters precisely.
Gate Delay
Set the time to wait after the gate signal is received before the gate
sweep is implemented. The gate delay is auto coupled to a
minimum value with different RBW values.
Gate Length
Set the gate length for gated sweep. The gate length is auto
coupled to a minimum value with different RBW values.
Gate Source
There are three sources for gated sweep.
When External is selected, a TTL signal is required.
For External and Periodic Timer, a sync source is
required for specified event synchronization.
RF burst is an internal trigger source if there is not any external
source.