Furuno DFF1 Digital Black Box Echosounder Module for NavNet (without Transducer) Works with NavNet and NavNet vx2 Wide variety of transducer options White line feature helps discriminate fish lying near the bottom Automatic function for detecting fish and bottom in both shallow and deep water DSP technology helps adjust gain and output power as well as suppresses main bang (echoes just below transducer) DSP technology helps adjust gain and output power as well as suppresses main bang (echoes just below transducer)