HP 54616B User And Service Manual page 61

Low frequency reject (LF Reject) adds a high pass filter with the 3-dB point at
50 kHz (see figure 2-20). Use LF reject to remove low frequency signals such
as power line noise from the trigger path.
Figure 2-20
0 dB
3 dB down point
dc
LF reject (trigger path)
Noise reject increases the trigger hysteresis band. By increasing the trigger
hysteresis band you reduce the possibility of triggering on noise. However,
this also decreases the trigger sensitivity so that a slightly larger signal is
required to trigger the oscilloscope.
Figure 2-21
Random noise on the displayed waveform
Pass
Band
50 kHz
Operating Your Oscilloscope
To reduce the random noise on a signal
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