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.
If the school's master clock stops, all the classroom clocks will become out of sync.
Compound of 親 (oya, 'parent; master') and 時計 (tokei, 'clock'). The reading おやどけい follows standard rendaku voicing of とけい to どけい in compounds.