Ricoh PRIPORT VT 2000 Series Service Manual page 59

28 February '91
VT2300/VT2500 Circuit in Line Mode:
VPH of Shading
Distortion
Memory
Black Level Correction
Output of Selector 1
Standard Voltage: 1.4
CN601-24
Density : 0
CN601-25
Density : 1
The printing density (i.e. image density) can be changed with the Printing
Density key on the operation panel.
Line Mode Selector changes the threshold level of VH (White level
reference) and VL (Black level reference) according to the density signals
from CN 601-24 and CN 601-25.
The A/D converter converts the analog input signal to a 4-bit digital signal
using both the white reference level (VH) and the black reference level (VL).
The following table shows the VH and VL levels that vary according to the
combination of the density signals in Line mode.
Printing
Density
Darker 2
Darker 1
Standard
Lighter
Line Mode
Setector
3
2
1
0
70%
3
40%
2
20%
1
0
A
Density Density
Signal 0 Signal 1
(CN601- (CN601-
24) 25)
H H
L H
H L
L L
Line/Photo
Selector 2
X
3
X
Y
Y
3
B
B A
SHMRT
PHTO
Line Mode Selector
ON Channel.
0X, 0Y
1X, 1Y
2X, 2Y
3X, 3Y
2-32
VH
4 bit
Image
Signal
VL
A/D Converter
A/D Converter
VH VL
100% 40%
100% 20%
100% 0 ~ 35%
70% 0%