Canon DADF-Q1 Service Manual page 60

Chapter 2
7) The host machine's scanner starts to scan the original as part of printing operation.
At this time, the machine picks up the 2nd original, and executes pre-reversal. (See steps 1 and 2.)
2nd original
8) When the host machine's scanner starts to move in reverse, the machine rotates the reversing roller and the transport belt to move the 1st and 2nd originals.
9) When the 2nd original has moved past the reversal sensor (S1), the machine rotates the transport belt over a specific distance and then stops the movement.
10) The host machine's scanner starts to scan the original as part of printing operation.
2-38
Pre-registration roller
paper sensor(S2)
2nd original
Reversal sensor(S1)
Scanning
(printing)
F-2-83
Scanning
(printing)
F-2-84
1st original
F-2-85
2nd original
F-2-86
F-2-87