Oki OKIPAGE 12i Service Handbook page 31

(2) Charging
Charging is actuated by the application of the DC voltage to the charge roller that is in contact
with the image drum surface.
The charge roller is composed of two layers, a conductive layer and a surface protective
layer, both having elasticity to secure good contact with the image drum. When the DC
voltage applied by the power supply exceeds the threshold value, charging begins. The
applied voltage is proportional to the charge potential, with offset of approximately –550V.
Power
supply
charge potential
[V]
-750
2 - 14
Charge roller
Image drum
-550 -1300
applied voltage
[V]