Agilent Technologies 81101A Reference Manual page 56

:PHAS[1]
[:SOURce]:PHASe[1][:ADJust]
Set & Query
Numeric
DEG or RAD. A parameter without a suffix is interpreted as RAD.
Programming the pulse phase also executes [:SOURce]:PULSe:HOLD
PHASe so that the pulse phase is held constant when the signal frequency
is changed.
Phase
Delay =
360
0.0
0 to 360 constrained by delay and period limits.
Use this command to set/read the relative phase delay of the output
signal. This is equivalent to setting an absolute or percentage pulse delay
with [:SOURce]:PULSe:DELay.
If you want the phase delay to remain constant when the pulse period is
varied (rather than the absolute pulse delay) use
[:SOURce]:PULSe:DELay[1]:HOLD PRATio.
To set and hold the phase delay:
:PHAS 180 DEG
:PULS:DEL:HOLD PRAT
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Period
Set OUTPUT phase to 180
Hold OUTPUT phase constant with varying
period