Ricoh Di-C1.5a Manual page 304

Both the trays are universal trays.
Paper size sensors: Detect the paper length
The position of the sensor actuator is controlled by the position
of the end fence
Slide 304
Only the length is detected directly.
The actuator has patterns of studs on the rear.
These studs turn the paper size sensors on/off.
This also tells the cpu that the tray is in the machine.
For a paper size detection table, see the service manual.
If other paper sizes are used, they must be selected with a user tool:
System Settings - Tray Paper Settings - Tray Paper Size (Tray 3, Tray
4).
Paper Size Detection
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