Increase the calibration if the other party experiences disturbing echo.
Decrease the calibration if the other party experiences low duplex, i.e. your voice is muted or clipped when the other party is speaking.
The position of the PA system’s microphones and speakers and the amplifier’s settings may affect full duplex performance.
AUTO is the default setting and is recommended in most cases. The figure shown in brackets ( ) is the measured calibration value.
Call someone and ask them to assess the effect(s) of any adjustment you make.