Ricoh FT4227 Manual page 258

12 February 1992 PROCESS CONTROL
After the ID sensor pattern is developed, the ID sensor checks the pattern's
reflectivity and the CPU notes it. If the reflected light is too strong, indicating
toner density is too low, toner is added to the development unit.
The toner is not added all at once. The CPU energizes the toner supply
clutch solenoid for the proper amount of time to add a calculated amount of
toner over the next 10 copy cycles (5 copy cycles for color toner).
Such toner supply control through the ID sensor is called a detect supply
mode. On this copier, this mode is used to control both black and color toner
supply.
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