Brother DCP7010 Service Manual page 59

When the new toner detection switch detects that the toner cartridge is replaced with a new one,
the developing bias voltage is initialized at the same time.
The toner used for the printer has a property that print density is light first and gradually darker in
the course of usage. The developing bias controls the toner property so that the print density is
constant from first to last.
Toner property
[Density]
[Voltage]
To always obtain a print result of a constant density, the printer counts the number of print pages
immediately after the toner cartridge is replaced and changes the bias voltage according to the
accumulated number of prints with the toner cartridge.
The bias voltage is changed with the steps described below:
(1) When the new toner sensor detects that the toner cartridge is replaced with a new (full) one,
the developing bias is set to 450V (initialized).
(2) After that, the bias voltage is stepped down according to the number of prints.
Counter reset during indication of "Toner Life End"
The counter resetting method during indication of "Toner Life End" depends on the cause of toner
life end and the condition of the inserted toner cartridge. Refer to the following table for details.
When a used toner is inserted
(Lever OFF)
When a new toner is inserted
Print density
Bias voltage
[Used toner amount]
Toner Life End
(Toner empty)
Toner exchange count: +0
Page counter of each toner: Continued
Coverage of each toner: Continued
Development bias: Continued
Toner exchange count: +1
Page counter of each toner: Reset (0)
Coverage of each toner: Reset (0)
Development bias: Reset (Default)
3 - 1 4
Actual control
[Density]
[Voltage]
Toner Life End
(Developer count full)
Not used.
Print density
Bias voltage
[Used toner amount]
Confidential