Car Home Subwoofer Equalizer Crossover Amplifier RCA Adjust Line Level Volume Remote Amplifier Level Controller This remote amplifier level control is used to adjust an amplifier's power level, stereo, equalizer or crossover volume form the dashboard or other remote locations 4 gold plated RCA's (2 RCA input & 2 RCA output) Level control knob, Frequency 150Hz - 40Hz, Gain 0db to -12db The car amplifier adds sub-woofer level controls or balances a multiple amplifier installation. Fine tunes the volume of any RCA line level signal you wish to control Simple in and out connections, no additional wiring needed