A wire rope is provided which has an independent wire rope core covered by a plastic jacket. A level flattening circuit for WDM optical signals is supplied with WDM optical signal and demultiplexs them into individual optical signals having different wavelengths, levels of which are separately feedback controlled to provide flattened optical signal levels. A plurality of ports are formed into the speaker enclosure base. The data can be stored in both a read-only memory for check in next use or temporarily stored in a dynamic random access memory for checking the data source of the result and the scale.