Toshiba V Series User Manual page 149

(4) Pay attention to the following cases caused by the diode mentioned in (3).
<Case 1>
When connecting to the external equipment in which DC power supply is provided
from internal, if the voltage of P1 is higher than one of P2 or if P2 turns to OFF
when P1 is ON, the external equipment may turn to ON in spite of the output
status.
Because a load current flows through D:a diode.
A power supply should be basically used for P1 and P2.
In the above case, insert a diode for preventing a back current in the position A so
that a back current is prevented from flowing into P2.
<Case 2>
When the power cable connected to the P24 terminal is cut off, external load may
be driven because the load current of OFF output circuit(OUT0) flows through the
diode and the transistor of ON output circuit(OUT1) as shown below.
Pay attention for preventing a P24 line from cutting off.
6F8C0836
DC Output module
D
OUT
A
P24
+
COM
DC Output module
OFF
ON
3.3 Precautions for DC Output Modules
External equipment
IN
P2
- COM
OUT 0
OUT 1
Cutting off
P24
COM
+
P1
-
Load
L
Load
L
24Vdc
127
3