Microsecond Clock Comparison by Means of TV Synchronizing Pulses

A new method for precise clocks comparison is described making use of the short rise time of the synchronizing pulse of a current TV picture signal. It is shown that by measuring simultaneously the time interval between one and the same selected TV frame synchropulse and the pulses derived from the respective clocks, these clocks may be compared with microsecond accuracy even if widely separated, provided that appropriate correction for the travel time of the synchropulse is applied. An experiment concerning international clock comparison between Prague and Potsdam is described, and the numerical results presented. Synchronization of clocks, separated by about 300 km, to about 2 ?s was accomplished, and it appears that 0.1 ?s is feasible. Further possible applications of this method are discussed.