| 摘要 |
In a high speed document printing system a hole mask circuit is provided to compensate for erroneous indications of the entry of additional documents into the system due to the sensing of a discontinuity or aperture within the body of a valid document. The hole mask circuit receives a document present signal from an associated sensor and employs a retriggerable timing means to inhibit the recognition of an additional document unless the sensor has previously signaled the continuous absence of a document for a preselected time interval. The circuit is capable of discriminating between a valid document having apertures of a preselected maximum size, documents having invalidly sized apertures and spacings between successive documents.
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