The Microphone (MCA-BTA) output signal is sent to the interface on two different lines:
1) A signal centered at 2.5 volts is on the standard 0-5V output line.
2) A signal centered at 0 volts is on the alternate +/-10V output line.

Here is a pinout diagram for the BTA connector:

Either line can be used to collect the microphone’s output; choose the line that best matches your DAQ device.