https://blog.gongquiz.com/2022/11/10/%eb%8b%a4%ec%9d%8c-%ec%a4%91-%eb%8f%99%ea%b8%b0%ec%8b%9d-%ec%a0%84%ec%86%a1sunchronous-transmission%ec%97%90-%eb%8c%80%ed%95%9c-%ec%84%a4%eb%aa%85%ec%9c%bc%eb%a1%9c-%ed%8b%80%eb%a6%b0-%ec%a0%95/