Hitachi WJ200 Series Quick Reference Manual page 94

As described on page 4-14 of this manual, inverter doesn't block the current flowing
into itself when it is not powered. This may cause the closed circuit when two or more
inverters are connected to common I/O wiring as shown below to result in unexpected
turning the on the input. This may lead to dangerous situation. To avoid this closed
circuit, please put the diode (rated:50V/0.1A) in the path as described below.
In case of Source logic
Short
bar
Short
bar
Switch
OFF
PLC
Short
bar
P24
Short
bar
1
Switch
OFF
Power ON
P24
PLC
L
Input
Inserting
ON
1
diode
Power OFF
P24
PLC
L
1
P24
L
Input
1
ON
PLC
L
Switch
OFF
Switch
OFF
92
Power ON
P24
PLC
L
Input
1
OFF
Power OFF
P24
PLC
L
1
P24
PLC
L
Input
1
OFF
P24
PLC
L
1