They are equipped with DCC (No Sound). All three are programmed to the cab number of the A unit, 1602. The shells are not attached to the A unit and one of the B units. The shells sit flush on the frame when placed on the track. There is a drawbar hanging off the back of the A unit that is intended to connect to B unit #2401 however I cannot figure out how.
Please let me know any and all questions you may have.