Abstract: A valve lifter, in which an amorphous hard carbon film is coated at least on the surface that slides against a cam, is characterized in that the surface of a base material (substrate) has an arithmetic mean roughness of Ra 0.01 to 0.03 micrometers, and the maximum length of the scratch on the base surface is made to be equal to or shorter than 250 micrometers.

Abstract: Specific information is registered to only a sensor, which is arranged adjacently to a base unit, by way of a radio output from the base unit. The radio output is a faint radio wave for short-range communications by which the base unit can be communicable with only the sensor adjacently arranged. Then, the specific information is registered to only another sensor, which is arranged adjacently to the sensor with the registered specific information, by way of a radio output from the sensor with the registered specific information. The radio output is a faint radio wave for short-range communications by which the communications can be made only between the sensors arranged adjacently to each other. The specific information registration is sequentially repeated between the sensors arranged adjacently to each other.