TH Marine TWA-1-DP Two Way Boat Alarm System Protects your Boat and Valuable Equipment from Theft Shock Sensor Detects Intruders and Alerts you up to 3000 Yards Away when Activated; Sensitivity Adjustment 128 db. Alarm Horn with up to 3000 Yards Response and 1000 Yards Transmit Two Way Remote Alerts with Sound, Light & Vibration Easy Installation of Waterproof Main Engine