Abstract: A base unit for supporting an infant carrier seat comprising a housing member having a bottom curved surface for rocking on a generally flat support surface, an upper central portion on which an infant carrier seat is removably mountable, an endless pathway that circumscribes said central portion, a weight and a motor to move along the weight in a closed loop at a selected predetermined rate of travel. The weight in the preferred form is a toy train unit with open topped box cars that removably hold a supply of weights. A sound generator on the train provides music and/or train whistle simulation. An infant can be entertained by the train travelling around the infant, by sounds generated by the train and the infant is rocked, all at the same time. The motion of the train travelling around the infant can be used to check responses of the infant as can also the movement of sound relative to the infant.