37
2TLC172001M0211_A
Output example 4:
Polarized safety relays
InA
Test
InB
0V
Q2
A
B
Q3
B
A
Monitoring
I_/IQ_
+24
/IQ_
When using a safety relay for output expansion of output Q2 and Q3, the connection between
the Pluto output and the safety relay is failsafe against short circuit from f24V. This
because it is operated by -24V and since the safety relay is polarized it cannot be switched on
by +24V. As long as a -24V potential does not exist in the cabinet (which is not normally the
case) the connection is failsafe.