Ricoh IM C300 Service Manual page 1481

If the battery jumper switch is not at the correct position, registering the fax unit will fail.
8.
Slide the FCU (PCB2) [B] into the slot along the guide rails [A].
9.
Attach the controller cover with the HDD removed in step 5.
10. Connect the harness to the FCU (PCB2) [A].
11. Open the line and telephone connector covers [A] with a flat-head screw driver.
12. Attach the left cover, upper left cover and rear cover.
D0CK 6
Fax Option Type M41 (D0CK02)
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