Master slave distributed clock arrangement - uses master clock emitting time check pulse daily or weekly to slave clocks running independently

摘要

The system includes a number of individual clocks (1) each of which has a circuit (42) for resetting them to the correct time in response to a received electrical signal. A high precision clock mounted centrally (42) emits daily or weekly pulses in order to correct the time displayed by the other clocks. The signal is emitted via the mains supply network, preferable between the phase and neutral lines of the supply. A ferrite ring (15) has a number of windings formed on it. The master clock provides pulses as input to one of these windings, while another secondary winding is connected via filtering circuits to the mains. The filter prevents the return of mains current, while allowing the transmission of the correcting time pulse. The pulse is detected by 'slave' clocks, and used to correct their displayed time.