... .Low noise compact form Industrial Centrifugal Fan Axial fan, Axial Flow Fan, Fan, Ventilator, Ventilation, Ventilating Fan, Ventilation, Ventilator Fan, Ventilation, Air Mover Application ... speed or guide vanes;· automatic switch of a stand-by fan at emergency switch-off of a running one;· ... automatic switch of stand-by low voltage input;· automatic restart of the fan drive at its disabling ...