When used in across-the-track configuration, Azatrax train detector circuits can be wired to two infrared sensor pairs. The detector will be 'on' when a train blocks either of the two infrared light beams.
 
Using two sensor pairs in this way will reduce the sensitivity of the detector. This normally does not cause a problem as long as the separation between each IrLED and its phototransistor (receiver) is less than 12 inches (30 cm) and the phototransistor is shielded from ambient room lighting.
 
Extra sensor sets are available with wire leads that are 2 feet (60 cm) or 6 feet (180 cm) in length. Leads are 24-gauge twisted pair, similar to telephone wire. You may extend the leads up to 25 feet (7.5 m) by adding similar twisted wire.