AR-FN5 (serv.man3). Maintenance Troubleshooting Circuti descriptions - Sharp Copying Equipment Service Manual (repair manual). Page 9

Any input signal from each sensor is connected to the pull-up resistor
(10Kohm) and the noise-eliminating capacitor (1000pF), and passed
through the buffer IC (74LS244) to the CPU input port.

This circuit detects open/close of the PG staple cover. When the cover
is closed, the contact is closed and the micro switch is closed.

The switches are connected in series to the +24V, forming the power
switch of the drive sections (the staple motor and the main motor).
Only when two micro switches are closed, +24V is supplied.

The tray cover switch is not treated as an interlock. When the cover is
open, it is not driven.

When the PG cover switch is open, staple cover open is not detected.

                                 Signal
  Status

PGSW

SCSW

Remark

Machine power interruption

d.c.

d.c.

PG cover SW open

L

d.c.

Stapler cover SW open

H

L

L: DOOR OPEN (or POWER OFF)
H: DOOR CLOSE (POWER ON)
d.c. unsettled (Since power is turned off on the upper side, 
       the status cannot be seen.)

5V

5V

1A1

2

1A2

4

1A3

6

1A4

8

2A1

11

2A2

13

2A3

15

2A4

17

1G

1

2G

19

1Y1

18

1Y2

16

1Y3

14

1Y4

12

2Y1

9

2Y2

7

2Y3

5

2Y4

3

20

10

CPU

74LS244

GND

VCC

1000pF/50V

UDZS5.6B

PHOTO

20K

0.1uF/25V

5V

5V

R8

D9

PG cover SW

Staple cover SW

+24V 

(To each motor)

C183
0.047uF/50V

C182
0.047uF/
50V

R9
1K/2W

D8
1SS133

0.22/2W

C193

0.047uF/50V

C194
0.047uF/50V

1SS133

20K

R177

R178
4.7K

C195
0.047uF/
50V

C196
0.047uF/50V

D11
1SS133

D10
1SS133

127

128

PGSW

SCSW

D13
1SS133

D15

1SS133

C198
0.047uF/
50V

C197
0.047uF/
50V

R180
4.7K

20K

R179

1SS133

D12

24V

CPU(IC1)

PG2

PG1