Introduced in the 40s, the defect detector came along to take the place of station agents and alert on-board crew of dangerous defects on the train. As a train passes through, the IR beams can detect dragging equipment, gauge temperature, monitor speed and send a signal to the dispatcher and train crew that something is wrong. Now you can add the action to your layout realistically with this all new accessory! The new detector counts your axles and delivers an announcement after the train passes providing an axle count, approximate train speed and the occasional defect! Use the max/min switch to set a high or low frequency of problems. Every lap around your layout brings a new chance for excitement!