Rockwell Automation T7446L_H ICS Regent+Plus Relay Output Modules - Manual (Page 3)

(T7446L, H) Relay Output Modules
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logically turned off, the relay coil is de-energized (closing the
N.C. contact).
The relay provides logic-to-field isolation between the
module’s logic and field circuits — protecting the output
module from field signal over voltages, transients, and other
electrical disturbances.
Both types of relay output module use UL 508 approved
relays.
Testing and Diagnostics
Each module’s voter circuits are periodically tested by the
processor modules. Discrepant data are sent through one of
three legs of the I/O Safetybus to determine whether the
module’s voter is able to outvote the incorrect data. A failure
to return the correct majority-voted result to the processors
produces an I/O module error indication at the processor
modules and a module fault indication at the I/O module.
Each type of module has a unique identification code that is
read by the controller. This code lets the controller know
which type of module is installed in each I/O chassis slot and
how to address that module and its points specifically. If a
module is removed, or is replaced with a module of a different
type, the processor modules will indicate an I/O module error.
Loopback logic tests periodically write data to the module and
then read it back to determine whether the module’s I/O bus
interface logic is functioning correctly.
Front Panel Indicators
The relay output module is shown in Figure 2. The front
panel contains active and fault status indicators, a shutdown
indicator, and output status indicators for each output circuit.
Active and Fault Status Indicators
These green and red LEDs indicate the overall health of the
module. During normal operation the green ACTIVE
indicator flashes at the controller's scan rate. If a module
fault is detected the red FAULT indicator turns on and the
green indicator turns off.