Simplify Crossing Signal Electronics with this Controller Fully assembled and easy to install with screw terminals, color-coded wiring and complete instructions. It includes the necessary optical sensors needed to activate the Walthers Crossing Signals in a realistic manner. Designed for use with a single track grade crossing, signals start flashing when the train passes the first sensor and turn off once it clears the crossing. Requires power pack or an 18V AC power supply, sold separately. NOTE: This unit is only for use on DC layouts - DCC systems can damage the controller.