A connector assembly is provided with opposing and interengageable first and second connector components. The electric motor controller includes driving stages for driving respective phase windings of the motor and a memory for storing samples of reference signals. A drive wheel assembly includes a drive wheel frame, a drive wheel disposed pivotally on the drive wheel frame, and a driving unit operable to rotate the drive wheel. The logic zero bias level applied to the laser diode is adjusted until the measured logic zero level of the optical signal reaches a first desired value. The address name processor includes a correlation processor, a correlation transceiver in communication with the correlation processor, and a response processor in communication with the correlation processor and the correlation transceiver. Thus, unevenness of exhausted gas can be suppressed at the right and left of the housing.