Replacment chassis for F units makes it easy to add sound and DCC to new or older units. Each includes a high quality digital decoder with motor control and a digital sound module on one circuit board. The sound is adjusted to the running mode: when the loco starts moving, you hear the primemover rev up and when it stops, you hear the engine slow down and braking sounds. All units come with a preprogrammed #72428 LokSound V.3.5, featuring the 16-cylinder_ EMD 567 prime mover, dynamic brakes, and a single chime air horn._ Can be used on DC layouts with a Precision Craft DCMaster #1001 Analog Control Module (sold separately) for pushbutton sound activation of bell and horn, volume control and programming. Sound units start at a slightly high voltage when operated on DC systems.