The Pro Series Boomsets are designed to meet the high standards of the most critical Multi-Op Contester and DX Chasers! Now we have added a speaker Phase Reversal switch that allows you to change the sound field between the two speakers. "In Phase", the signal is centered in your head so you can 'see' it better. "Out of Phase", the signals are spatially widened so they are easier to pick out of a pileup up. This exclusive feature greatly reduces listening fatigue, reduce noise and enhance intelligibility.