Boston Acoustics 120-003452 MCS 160 Subwoofer Power Supply/Rear Panel Power supply/rear panel for Boston acoustics MCS 160 Subwoofer On/Off switch, Adjustable volume knob, 0 - 180 degree adjustable polarity switch Line in port, Integrated power cord LED indicator light between the Power switch and the Polarity switch indicates what mode the subwoofer is in Positive (Red) and negative (Black) cables (located in back of unit)