Building on their inventions, Su Song of the Northern Song dynasty designed an even better water-driven astronomical clock tower with an armillary sphere and celestial globe, which used an escapement to control the movement of the gears, enabling the whole device to keep time accurately and to turn in synchrony with the stars.
北宋蘇頌在他們的基礎上，設計出更為完善的「水運儀象台」，他利用一卡一放的擒縱系統來控制齒輪，使整座機械裝置得以準確計時，並與星體同步運轉。