Rockwell Automation T3468A ICS Regent DC Guarded Digital Output Modules - Manual (Page 10)

DC Guarded Digital Output Modules (T3461A, 62A, 68A)
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Industrial Control Services
module. In this way, the two FETs of each output circuit are
connected in series with the load: one on the positive side and
one on the negative side of the load.
The output loads must not connect to the field power supply
return out in the field. Such connection will bypass the
negative-side FET in the Guarded output and defeat the
purpose of the two series FETs for fail-safe or fault tolerant
control.
Output circuit testing requires the presence of field power on
terminals A/B and C/D. If output power is disconnected,
output testing fails and a module fault is indicated.
Important!