DZ-1040LV Semaphore Lower Quadrant | O gauge

Exclusive optical sensors in the base of each signal detect an adjacent train.

Just set them down and connect 2 wires to power for a working signal.

When the train passes the signal, the indication will change to RED or stop and hold until the train has passed. 4 seconds after the train passes, the signal will change to YELLOW or caution.

After 3 more seconds, it will change back to GREEN or clear.

The indicating flag moves realistically slow. 

The signal only needs (9-18V AC or DC) power to operate, but it does have an input (YELLOW) and an output (WHITE) for additional possibilities.