Fujitsu Ricoh Fujitsu N7100E Network Image Scanner - Manual (Page 467)

Glossary
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Threshold
The value which is used to determine whether a certain color is black or white.
Threshold value must be configured in order to scan images with grayscale
gradation. Each pixel is converted into black or white according to the specified
value.
Ultrasonic sensor
A type of sensor that uses ultrasonic sound waves, in this case to detect
document multifeeds by recognizing differences in how the sound penetrates
single versus multiple sheets.