親おや時計どけい

noun

master clock; control clock

Technical term for the central clock that synchronizes other clocks in a system, such as in a school, factory, or radio-controlled clock network.

• 学がっ校こうの親おや時計どけいが止とまると、すべての教きょう室しつの時計とけいがずれてしまう。

  If the school's master clock stops, all the classroom clocks will become out of sync.