Stanford Research Systems SR530 Manual page 10

Phase Controls Adjust phase in smoothly accelerating 0.025° steps, or by
90° steps. Press both 90° buttons to zero the phase.
Reference LCD Display reference phase setting or reference frequency
Time Constants Pre-filter has time constants from 1 mS to 100 S (6 dB/Octave)
Post-filter has time constants of 0, 0.1 or 1.0 S (6 dB/Octave)
ENBW Equivalent Noise Bandwidth. Specifies the bandwidth when making
Noise measurements. (1Hz or 10 Hz ENBW)
Power Switch Instrument settings from the last use are recalled on power-up
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