Canon Color iR C3480 Service Manual page 244

Chapter 7
UN14. (See Notes.)
The machine executes gradation correction for all colors, regardless of which drum unit may have been replaced.
ITB
UN16
Laser Scanner
unit
[1]
[4]
D-CON
[2]
[3]
M-CON
F-7-25
[1] Patch image data
[2] Density data
[3] D-half control
[4] Video data
UN16: patch image sensor
3. Flow of Operation
7-21