ROLLS DU30b Audio Ducker Automatically ducks music under announcements Perfect for restaurants and small clubs Clean, Quiet Mic Preamp REAR PANEL MIC IN: Female XLR jack for connection to a dynamic or condenser paging microphone. PHTM PWR: Jumper for engaging the +12 volt phantom power to the microphone input - configured OFF from the factory. AUX IN: Stereo RCA jacks for connecting to a source different from the Mic In as the master signal. LINE IN: Stereo RCA jack for connection to the stereo signal source to be "ducked" such as a tuner, CD player or cassette player. OUTPUT: Stereo RCA jacks for connection to the system's amplifiers. 12 VDC: Power input. Connect to the enclosed Rolls PS27 AC adapter. The DU30b is a microphone preamp and background music preamp. When an announcement is made into the microphone, the music is automatically "ducked" under the announcement. Then the music is brought back to it's previous level.