Canon IMAGEFORMULA CR-190I - Manual (Page 33)

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Using Ultrasonic Double Feed Detection
The double feed detection function that the scanner is equipped with
uses the penetration of ultrasonic waves to detect when two or more
documents are fed at the same time.
If false detections happen too often, disable the double feed detection
function.
NOTE
When Using the Accompanying Scanning Utility for CR-190i:
You can disable the double feed detection function to push the Function
Button. When the function is disabled, the light of the Function Button is
off.