Centralised clock system for large buildings - has digital information transmitted between master clock and slave clocks

摘要

The information is transmitted between the digital master clock and each slave clock as a binary decimal code. The master clock (1, 2, 3, 4, 5) is associated with a pulse generator, (6) operating to periodically send a high frequency pulse train down the two wire line (7) connected to each slave clock (9, 8). The number of pulses in the pulse train correspond precisely to code of the master clock at that instance, with each slave clock having means for generating a code for control of the slave clock from the pulse train. Pref. a counter responds to the pulses sent down the line and the count is compared at each instant with a parity table, with the pulses blocked if parity between the pulse train and the table is not obtained.