Intermatic LC4521C 120-Volt Locking Type Thermal Photocontrol Locking style thermal photocontrol provides dusk-to-dawn ON/OFF control of exterior lighting, street lighting, parking lot, pedestrian pathway and landscape lighting Delay feature prevents unwanted OFF switching of lights due to passing car headlights or lightning Twist lock plug for quick installation and changeover features integral high-impact thermoplastic housing Features a cadmium sulfide photocell and a mechanical bimetal switch Not for use with LED lights