Canon imageRUNNER ADVANCE 4551i Service Manual page 70

PS_A6
Detection in the Width Direction
The size is determined by the Original Size Sensor (UN_BO6).
● Original Detection Control
Detection of originals in the Document Pickup Tray is performed by the Original Sensor (PS_N1).
When an original is placed in the Document Pickup Tray, the Detection Lever operates with the Lightproof Plate and the Lightproof
Plate passes through the Photo Interrupter. This makes the Original Sensor (PS_N1) emit an original detection signal (EMP_S).
If the Cover Open/Closed Sensor (PS_A5) detects that the Feeder Cover has been closed, a Feeder Cover open/close detection
signal (COVER_S) is emitted.
When the ADF Driver PCB receives a Feeder Cover open/close detection signal (COVER_S) and original detection signal (EMP_
S), an original set indication signal (EMP_LED) is sent to light the Original Set Display LED (LED).
ADF Driver PCB
PS_R1
UN_BO6
ADF Driver PCB
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2. Technology