A technique by which when printing is initiated, printed sheets remaining in a large-volume stacker and sheets printed in a subsequent job are not mixed in the large-volume stacker is provided. A printing system in which a printing apparatus and a post-processing apparatus for receiving a sheet printed by the printing apparatus and performing post-processing are connected, upon activation of the printing system, when detecting that a sheet is stacked in the post-processing apparatus, instructs the processing apparatus to discharge the remaining sheet.

A technique by which when printing is initiated, printed sheets remaining in a large-volume stacker and sheets printed in a subsequent job are not mixed in the large-volume stacker is provided. A printing system in which a printing apparatus and a post-processing apparatus for receiving a sheet printed by the printing apparatus and performing post-processing are connected, upon activation of the printing system, when detecting that a sheet is stacked in the post-processing apparatus, instructs the processing apparatus to discharge the remaining sheet.

An automatic document feeder includes a media path to route media through the automatic document feeder, a plurality of opposing roller pairs to route media along the media path, and a serpentine belt drive system to drive a roller of each of the opposing roller pairs.

An automatic document feeder includes a media path to route media through the automatic document feeder, a plurality of opposing roller pairs to route media along the media path, and a serpentine belt drive system to drive a roller of each of the opposing roller pairs.

A paper feeding device includes a pickup mechanism, a conveying mechanism disposed behind the pickup mechanism, a separation mechanism disposed behind the conveying mechanism, a feeding mechanism disposed behind the separation mechanism, a transmission mechanism driving the pickup mechanism, the conveying mechanism, the separation mechanism and the feeding mechanism, and an ultrasonic circuit unit disposed between the separation mechanism and the transmission mechanism. The ultrasonic circuit unit includes an ultrasonic detecting module, an amplifying circuit unit electrically connected with the ultrasonic detecting module, a paper density detecting unit electrically connected with the amplifying circuit unit, an analog-to-digital converter electrically connected with the paper density detecting unit, a processor electrically connected with the analog-to-digital converter, and a driving unit electrically connected with the processor and the transmission mechanism.

A paper feeding device includes a pickup mechanism, a conveying mechanism disposed behind the pickup mechanism, a separation mechanism disposed behind the conveying mechanism, a feeding mechanism disposed behind the separation mechanism, a transmission mechanism driving the pickup mechanism, the conveying mechanism, the separation mechanism and the feeding mechanism, and an ultrasonic circuit unit disposed between the separation mechanism and the transmission mechanism. The ultrasonic circuit unit includes an ultrasonic detecting module, an amplifying circuit unit electrically connected with the ultrasonic detecting module, a paper density detecting unit electrically connected with the amplifying circuit unit, an analog-to-digital converter electrically connected with the paper density detecting unit, a processor electrically connected with the analog-to-digital converter, and a driving unit electrically connected with the processor and the transmission mechanism.