Counter Input >> Position >> A Input >> Terminal

NI-DAQmx C Properties

Counter Input >> Position >> A Input >> Terminal

Data Type: char*
Description: Specifies the terminal to which signal A is connected.

You can get/set/reset this property using:
  DAQmxGetCIEncoderAInputTerm
  DAQmxSetCIEncoderAInputTerm
  DAQmxResetCIEncoderAInputTerm