Vorrichtung zur Detektion von Blätter

摘要

An ultrasonic signal is fed through a position occupied by a sheet, e.g. being supplied to a printer, copier or ATM. The phase of the signal passing through the sheet is compared with that of a reference signal from a signal generator to produce a signal with a level corresponding to the detected phase difference. This signal is then compared with a stored reference signal to determine whether more than one sheet has passed through. When a single sheet is fed a high level signal is produced but when a double sheet is fed a low level signal is produced.