National Instruments NI 9411 Operating Instructions And Specifications page 13

An example of a single-ended device is a single-ended encoder.
A single-ended encoder has phase A, phase B, and index signals.
Use the phase A signal to measure rotational speed. Use the
phase B signal to measure direction. Use the index signal to
measure the number of rotations.
Connect each of the signals of the encoder (phase A, phase B,
and index) to a DI pin. Figure 5 shows the connections for
one single-ended encoder.
NI 9411 Operating Instructions and Specifications 12 ni.com
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