Bit lines formed from a first metal wiring layer and bit lines formed from a second metal wiring layer are provided as bit lines that intersect with word lines. The method and apparatus include moving the carriage in a second direction towards the home position until the carriage is not moved for a second predetermined period of time and determining a current position of the carriage as a second position. Such sensing means allows the diaphragm to move freely without mechanical coupling to a secondary transducer, while providing a direct and efficient acoustic to electrical conversion means. A change in the posture or position of the base bodies is offset with a swinging movement by the holding section, and does not affect the guide rail. For example, the input optical signal may be a wavelength division multiplexed signal carrying multiple channels on different wavelengths, and the tunable multiport optical filter directs one of the channels to the output optical port.