A very precise short-period comparator for 100 kc/s frequency standards

An instrument is described for the very precise comparison of 100 kc/s frequency standards. A sensitive phase-comparator is combined with a trigger circuit to produce a timing pulse at the instant the two 100 kc/s signals are in phase opposition. The time interval between successive pulses is determined by a counter-type chronometer. For a 10 sec beat period a timing accuracy of 1 microsec is obtained. This corresponds to an accuracy of frequency comparison of 1 in 1013.