Rockwell Automation T3418F ICS Regent Monitored Digital Input Modules, Field Powered (Type F) - Manual (Page 14)

Monitored Digital Input Modules, Type F (T3411F, T3418F)
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Industrial Control Services
Line Monitoring
For DC powered inputs, the monitored digital input module
can perform line monitoring of the field wiring when a
suitable line monitor device is installed across the field input
switch. A variety of line monitor devices are available to
match the voltage and input redundancy used in the
application.
Figure 8 shows a single switch connected to a single monitored
input module. This type of configuration uses a line monitor
device which contains two resistors, one in series with the field
switch and one in parallel with the field switch. Figure 8 also
applies to fault tolerant input configurations that include
redundant sensors connected to redundant input modules.
Figure 8. Line Monitoring, Single Switch Connected to
Single Module.