https://qooah.com/2011/12/28/lg%e6%97%97%e8%89%a6%e7%b4%9a%e6%89%8b%e6%a9%9fspectrum-%e5%8d%b3%e5%b0%87%e4%b8%8a%e5%b8%82%ef%bc%81/