Grade Crossing Flasher Circuit works on single or double track. It may be operated by reed switches, IRDOT infra red detectors, or manually with a switch. Requires a 12 volt supply, DC or AC. Includes two pairs of LEDs for the crossing lights. While the lights are flashing, an on-board relay is activated to operate gates moved by a slow motion switch motor (not included). Circuit board is 2-1/2 inches wide x 3-1/4 inches long.