Hardware reference guide

I/O Modules
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Discrete I/O True High/True Low Circuit Descriptions
The following figures illustrate discrete I/O module true high and true low logic
circuits.
Current Sinking describes a physical implementation of the I/O hardware, which
when in the true state, sinks current from the external load.
Current Sourcing describes a physical implementation of the I/O hardware, which
when in the true state, sources current to the external load.