KX-MC6020RU, KX-FAP317A, KX-FAB318A - Panasonic Fax Service Manual (repair manual). Page 122

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The charging roller, comes in contact with the OPC drum surface and charged to approximately -1100 volts, and ensures a uniform
negative potential of approximately -500 ~ 550 volts on the OPC drum surface by the charging roller, depending on the selected dot
per inch printing and ambient temperature. 

As the OPC drum rotates, the uniformly charged OPC drum is exposed by the modulated laser beam. The vertically-moving OPC
drum passes in front of horizontally scanning laser beam, and the negative charge on the OPC drum surface are neutralized by the
laser beam. This forms a latent image.
Laser output power is either approximately 0.3 mW or 0.5 mW on the OPC drum surface, depending on whether the printer is print-
ing in 1200 dots per inch (dpi) mode or 600 dpi mode. The laser exposure, the negative potential on the OPC drum varies from
approximately -500 ~ 550 volts (unexposed) to -50 volts (fully exposed).

1.Charging (See P.122)

5. Paper Pickup (See P.124)

2. Laser Exposure and Scanning (See P.122)

6. Toner Transfer to Paper (See P.125)

3. Developing (See P.123)

7. Fusing (See P.126)

4. Toner Transfer to the Accumulator Belt  (See P.124) 8. Paper Exit and Paper Switchback (See P.127)