Provided with two Opto-Sensors, the flasher outputs will be one when either is shaded. Drives LEDs or lamps (250mA per side). Also directly powers a Tortoise (not included) for gate activation. Does not detect short trains falling between sensors. One additional sensor can be added, but will reduce sensitivity. Adjustable for light intensity. Not for very low-light situations. 10-18V AC or DC input. Add DT-5 for additional track.