4. THEORY OF OPERATION page 18
Model PRM-470B
If the moving average sum equals or exceeds this threshold, the audio alarm will sound
momentarily. The audio alarm may also sound momentarily when the display is below the alarm
threshold, since the display is updated every second, while the alarm comparisons are made
every 50 milliseconds.
4.5. AUDIO ALARM
The audio alarm is a piezoelectric type. It is activated to signal the start of the self-test or an
alarm condition.
The rate at which the audio tone repeats is dependent on intensity of the radiation field. The
frequency is constant.
The alarm LED is also illuminated with the audio for use in high noise areas.
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