The units feature signals with flashing LEDs and digital sound. The Crossing Signal Set includes a pair of dwarf-style DZ-1011 Block Signal Detectors that optically detect trains up and down track in addition to the optical detection at the crossing. Up to four tracks can be independently sensed with additional DZ-1011 Block Signal Detectors. • For S guage - sink base into table layout. • Realistic scale proportions • Optical train detection ( no cutting of rails required) • Realistic, long-life, red and green LED signals • Digital crossing bell sound • 2 DZ-1011 Block Signal Detectors included • Handles up to four tracks