The Broadway Limited Rolling Thunder Receiver and Subwoofer Kit brings realistic locomotive sounds to your HO or N Scale railroad. The system works with sound and DCC decoders installed in Broadway Limited Paragon3 locomotives to deliver low-frequency sounds through a layout-based subwoofer mounted under the layout while your locomotive′s on-board speakers handle the higher-frequency sounds. The result is that while the locomotive moves around the layout, you can hear the high frequency sounds coming from the locomotive, and the low frequency sounds from the subwoofer - all perfectly synchronized to the motion of the locomotive and the puffing of the smoke, and your ears will perceive the full array of sound as coming from the model! The system will work only with Paragon3 decoder-equipped locos on any DCC or DC layout although locomotive sound functions may be limited on DC systems. Rolling Thunder systems are optimized for their noted scale. The Rolling Thunder complete system includes the receiver unit and a powered subwoofer.