Master Lock 4840DATSEN Trailer Sentry Boat Trailer Anti-Theft Alarm System Provides electronic security through a 110 decibel alarm siren that sounds when the trailer wiring is cut or disconnected and acts as a power module to deliver needed power directly to the trailer from the vehicle battery Alarm mounts under the hood and power module mounts under the vehicle with a voltage sensor to prevent battery run down and detects if a light is burned out Revolutionary theft protection for your boat trailer is fully submersible Trailer lights can be disconnected via the remote while trailer is submersed in water, features remote lighting cut-off Includes 1 fob, simple installation