Undecrated w/ Dynamic Brakes with DCC and Sound. Model is limited to supplies! QSI® Quantum System™ Features Including: Dual speaker system Authentic diesel engine sounds Squealing brakes Doppler effect Air let-off in neutral Coupler impact sounds when operated with DCC Helper mode that mutes the whistle and bell for double heading And more! Note: Due to the higher starting voltage required to operate the sound system, it is not possible to MU a non-sound-equipped loco in DC (analog) mode