HP 8901B Operation And Calibration Manual page 287

Operation
Model 8901B
COMMENTS
Functions That Override Audio Input
The Audio Input function is overridden by all measurements except audio frequency, distortion, SINAD,
and external level.
Errors Disable Output Signal
Errors 0 1 through 03,05,10, and HP-IB Error
96
(corresponds to a display of two dashes) turn off the
signal at MODULATION OUTPUT/AUDIO INPUT.
Default Condition
When the Modulation Analyzer is first powered up, the demodulated output signal at MODULATION
OUTPUT/AUDIO INPUT is FM. The sensitivity is 0.01 mV/Hz (the least-sensitive range) and will
not autorange
to
more sensitive ranges. This is because
at
power up, FREQ is selected. Thus Error
04
(audio circuits overdriven) is automatically disabled. When Error
04
is disabled, only autoranging to
less-sensitive audio ranges is allowed.
Safeguarding Output Signal
When Errors 01 through 04 are always enabled via Special h c t i o n 8.8, the output signal at MOD-
ULATION OUTPUT/AUDIO INPUT
is
entirely safeguarded. Under this condition the instrument
operates as a calibrated receiver and an error is displayed whenever the signal at MODULATION
OUTPUT/AUDIO INPUT is uncalibrated. (Refer to Error Message DisubZe Control on page 3-233.)
Filters Affect Output Signal
The audio high-pass and low-pass filters and FM de-emphasis affect the output but not the input of
the MODULATION OUTPUT/AUDIO INPUT.
3-190
Modulation Output/Audio Input