Rockwell Automation T7488/T7488A ICS Regent+Plus Monitored Guarded Output Modules - Manual (Page 9)

Monitored Guarded Output Modules (T7481/81A, 84 and 88/88A)
P D - 6 0 3 3 M a r - 0 6 (Issue 2)
9
Output Status Indicators
The output status indicators are yellow LEDs, located on the
front of the module. The state of the output circuit is sensed
on the field side of the output circuit and optically coupled to
both of the FPGAs. The FPGAs logically drive the output
status LEDs. The indicator is on when the output circuit is
energized.
During output testing, the module monitors the current flow
to the load device. If no current is detected, or if an excessive
current is detected, the red load/fuse fault LED is energized.
This indicator annunciates a blown fuse or an open or short
circuit in the field wiring to the output field device.
Application
Monitored Guarded digital output modules provide a suitable
interface to safety-critical output devices. These safety-
critical devices typically include solenoids, actuators, or other
process interlock outputs. Monitored Guarded output modules
can be used for fail-safe or fault tolerant operation.
Fail-Safe Configuration
As shown in Figure 3, fail-safe configuration uses a single
monitored Guarded output module. In this configuration, the
worst case failure will cause the output to fail to the off state.
In a fail-safe configuration, removing the module disables all
outputs.
Figure 3. Fail-Safe Configuration.