dSC-F4 / SC-F3 Gold-plated screw connectors for speaker and power supply cablesAutomatic car radio-controlled on/off switchingLED power and overload indicatorTrimode speaker operationVariable subwoofer filter (50-250 Hz, 12dB I oct.)Bass Boost switch (+6dB at 45Hz)Short circuit thermal overload protection SC-F2 / SC-F1 Gold-plated screw connectors for loud speaker and power supply cablesAutomatic car radio-controlled on/off switchingLED power and overload indicatorBrid