An insulating resin for switch gears on the basis of glycidyl ester contains methyl nadic anhydridehydrogenated methyl nadic anhydride as hardener and an N-substituted imidazole as accelerator. A cutting head is slidably mounted within the duct adjacent to the air port and is adapted to clean the air port. In response to the detection voltage signal and the first reference current, a transfer unit determines a first operation voltage. An integrated casing encapsulates the microphone sensors and the analog processing circuit, and prevents external interference from affecting any electrical signals within the integrated casing. The signal at the desired frequency may be multiplied by the selected local oscillator frequency to down-convert the signal. According to the identifying information of the second information included in the request statement, the information providing resource determines whether or not transmission of the second information to an information providing unit is allowed.