Ricoh SP 8400DN Field Service Manual page 1396

7.Detailed Descriptions
If the difference between the TD sensor output and the target value is less than the near end threshold twice in a
row, the toner near end indicator is turned off.
If the difference between the TD sensor output and the target is equal to or larger than the end threshold, the
machine detects that a "possible" toner end exists. As the machine continues to operate, it starts to calculate an
integrated value. If the integrated value is equal or larger than the toner end total threshold, the machine
determines that a "true" toner end exists.
Toner End Recovery
In a toner end condition or toner near end condition, if the front cover is kept open for more than 5 seconds and
then it is closed, the machine changes to a toner end recovery mode. You must keep the main power on when you
replace the toner bottle or toner end recovery will not work.
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