Rockwell Automation T7411F ICS Regent+Plus Monitored Digital input Modules, Field powered (Type F) - Manual (Page 12)

Monitored Digital Input Modules, Type F (T7411F, T7418F)
1 2
Industrial Control Services
Figure 7 shows a single switch connected to a redundant
monitored input modules. This type of configuration uses a
line monitor device which contains two zener diodes, one in
series with the field switch and one in parallel with the field
switch.
Figure 7. Line Monitoring, Single Switch Connected to
Redundant Modules.