Rockwell Automation Publication 1734-UM013C-EN-P - August 2010 31
Safety Functions Chapter 2
Table 2 shows the expected behavior of the muting status for test outputs T1 and
T3. Keep these points in mind as well:
• When power is applied to the 1734-IB8S module, and T1 or T3 remains
commanded off, the muting status defaults to on.
This bit operation is designed to help prevent erroneous muting
instruction faults from the GuardLogix controller. This bit status may not
be the true indication of a burned-out lamp.
• If a muting lamp circuit is open when power is applied to the module, the
condition will be detected when the test output is commanded on.
• When a lamp burns out and is replaced, the fault (muting status bit) will
return to the normal condition, independent of the state of the test output.
Before checking the state of the corresponding muting status, be sure the
test output is commanded on. Once the test output is commanded on, a
maximum time of 6 seconds is required for the module to detect a
burned-out lamp.
Table 2 - Muting Status Bit Operation
Test Output Commanded State Lamp Condition Muting Status Bit Description
ON Bad (open circuit) 0 Repair lamp.
ON Good 1 Normal condition. Lamp is operating properly.
OFF Bad (open circuit) 0 If lamp remains OFF after T1/T3 output cycled, repair
lamp.
OFF Good 1 Normal condition.
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