Kyocera FS-1900 Service Manual page 111

The paper size dial has predetermined patterns of activating the paper size switches using concaves
and convexes according to paper sizes. SW1, SW2, and SW3 produce corresponding signals for
paper sizes. These patterns are translated into analog voltages and sent to the engine board on a
single line. The signals are analog-digital-converted on the engine board.
Engine board
CPU
(U204)
Cassette
Paper size switch
SW1
SW2
SW3
D/A converted
output voltage
Note: Toner install mode cancellaton signal (See page 3-14)
FS-1900
Sensor board
+24V1
R701
DZ70
GND
C246
R238
GND GND
Paper size
Custom
not Letter
installed
Off Off Off
Off Off On
Off On On
0 V 1.94 V 1.58 V
Approximately
Figure 4-3-14 Paper size detecting circuit
SW1
SW2
SW3
Paper size switch
Legal A4 A5 B5
Off On On On
On Off Off On
Off Off On Off
1.19 V 0.42 V 2.28 V 2.92 V
4-36
Paper cassette
Paper size dial
See
note
below.
On
On
Concave
(Function Off)
On
Convex
(Function On)
3.22 V
Paper size dial