C7085-90921 Chapter 5 Theory of operation 125
Last paper detected
The printer detects the last page of the print job before writing the next image. This prevents toner
particles from smearing on the photosensitive drum and ITB.
To detect the last paper, the last paper sensor (PS3) monitors the rotation of the last paper detection
roller on the multi-purpose tray. If there are two or more sheets in the multi-purpose tray, the last
paper detection roller does not rotate when one sheet is picked up. Once the last paper is picked up,
the last paper detection roller rotates. PS3 monitors this rotation, and a warning message is sent to
the control panel.
Figure 5-28 Laser paper detected
Overhead transparency detection
Overhead transparencies (OHT) are detected by the OHT sensor (PS301) located at the front of the
registration roller. Light is emitted from PS301 and passes through the paper path, reflected by the
reflective mirror, and returned to PS301. As paper passes over PS301, the light emitted from PS301
is blocked by the paper and thus does not return to PS301. Transparencies are detected when the
light passes through the OHT which is reflected by the prism, and returns to the sensor. The printer is
then switched to OHT mode and changes the paper path speed during transfer and fusing.
Figure 5-29 Overhead transparency sensor
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