... & construction 3.good quality,low price Speed Controller for In-line Duct Fan 120V/230V is available. ... professinal manufacturer of ventilation products including FAN, SPEED CONTROLLER, CARBON FILTER,PIPE FITTING, ETC in China. ... to visit our Group Company at any time. For variable speed control set the rocker switch (8 ... (10) to low, medium, or high speed.For full speed operation, set the rocker switch (8 ...