Check the listing for details. Master Lock Trailer Sentry Anti-Theft System 4840DATSEN. Condition: New. Listed at 32.99 USD. Description Master Lock 4840DATSEN Trailer Sentry Boat Trailer Anti-Theft Alarm System provides a new way to secure a trailer to a vehicle by continuously monitoring the trailer's lighting circuit and triggers a remote alarm if the trailer is disconnected from the vehicle or if the wires are cut. It works alongside any mechanical security devices to offer a new level of security and convenience. 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 batteryAlarm 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 outRevolutionary theft protection for your boat trailer is fully submersibleTrailer lights can be disconnected via the remote while trailer is submersed in water, features remote lighting cut-offIncludes 1 fob, simple installation