Apparatus for measuring a difference in time intervals of a timepiece

Claim 1

Apparatus for measuring the out-beat of a watch, clock or the like by measuring the difference between the duration of a first pulse interval of an impulse series produced by the watch, clock, or the like and a second pulse interval of said same impulse series comprising, a reversible digital counter, gating means at times responsive to said impulse series and at times to the attainment by said counter of a zero count for selectively producing a positive count gate pulse and a negative count gate pulse, and said single source of trigger pulses applied to said counter and occurring throughout the total durations of said first and second pulse intervals, said gating means producing said positive count gate pulse and controlling said counter to count said trigger pulses in a positive sense during said first pulse interval and producing said negative count gate pulse and controlling said counter to count said trigger pulses in a negative sense during said second pulse interval, said gating means further being responsive to the attainment by said counter of a zero count during said second pulse interval for again producing said positive count gate pulse and controlling said counter to count said trigger pulses in a positive sense over the remainder of said second pulse interval, whereby the count in said counter at the end of said secOnd pulse interval corresponds to the difference in durations of said first and second pulse intervals irrespective of which is the longer.