A protective coating for a surface exposed to hot gas flow comprises a thermal layer, a conducting layer and an abrasive layer. A set of Doppler signals are acquired of the ultrasonic signal after reflection by the object. The display unit displays a control panel of the controlled device. The same color as referred to herein means that the chromaticity coordinate values are equal to each other. An upper portion of the breather filter is tightly coupled to the cover and a lower portion of the breather filter is tightly coupled to the base.