| 摘要 |
PROBLEM TO BE SOLVED: To provide a duplicate feed detecting device for properly adjusting signal intensity of an ultrasonic wave received signal by controlling a transmitting method and a receiving method of an ultrasonic wave without changing a constitution of a signal amplifying means or adjusting an amplification factor. SOLUTION: An ultrasonic wave transmitter 2 is arranged in one for sandwiching a carrying passage of paper 1, and transmits an ultrasonic wave in the direction of the paper 1. An ultrasonic wave receiver 3 is arranged in the other for sandwiching the carrying passage of the paper 1, and outputs an ultrasonic wave received signal by receiving the ultrasonic wave transmitted by the ultrasonic wave transmitter 2. A control means 4 controls the acquiring timing of the ultrasonic wave received signal and/or a characteristic of the ultrasonic wave transmitted by the ultrasonic wave transmitter 2 for adjusting amplitude of the ultrasonic wave received signal outputted by the ultrasonic wave receiver 3. A signal analyzing means 8 analyzes whether or not to be a duplicate feed on the basis of a change in the amplitude of the ultrasonic wave received signal adjusted by the control means 4 and outputted by the ultrasonic wave receiver 3. COPYRIGHT: (C)2004,JPO&NCIPI
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