The J06-59992A is a special instrument used to increase the accuracy of precision time interval measurements. When employed to determine the systematic errors of a particular measurement set-up, the calibrator can provide for absolute accuracy on the order of +/- 100 ps when making the time interval measurements with the HP 5371A/B Time Interval Counter. The calibrator can be used to improve the accurance of the HP 5363B Time Interval Probes when used in conjunction with the HP 5370A/B Counter.