HP 54710A User's Reference Manual page 293

Trigger Menu
Mode
Delay time
Delay time has the oscilloscope arm on an edge from one of the channel or
trigger inputs, wait for a selected period of time, then trigger on an edge
from any of the channel or trigger inputs. Basically you can think of delay by
time as two edge triggers that are separated by a selectable time.
The traditional method to view events that happen after the trigger event is
to use time base position to pan through the data. The problem with this is
that the further the point of interest is from the trigger event, the greater the
possibility that jitter makes it difficult to analyze the point of interest.
Delay by time eliminates this problem because it moves the trigger event
closer to the point of interest which reduces any jitter on long delay
measurements.
For example, a disk drive motor does not spin at a constant speed all the
time. If you use time base delay to look at a pulse separated from the trigger
event by a long time period, the jitter on the pulse caused by variations in the
motor's speed can make it almost impossible to see the desired pulse. Delay
by time allows you to delay out to the pulse of interest, then trigger on that
pulse. Because you are triggering on the pulse of interest, jitter is not a
factor in viewing the pulse.
Arm on Selects the slot, trigger level, and slope for the arming
conditions of the trigger circuitry.
Delay Used to set the delay time from 30 ns to 160 ms.
Trigger Selects the slot, trigger level, and slope for the trigger event.
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