SYSTEM FOR MEASURING INSTANTANEOUS FREQUENCY VALUES

An incoming oscillation, whose frequency during a brief reading interval is to be determined, is converted into a first pulse train of cadence f to be compared with the cadence f' of an astable multivibrator responsive to a stored control voltage. During the reading interval the control voltage is modified by a signal depending upon the difference of the two cadences until the same are identical; during an adjoining extended storage period, the modified control voltage keeps the multivibrator operating at the unknown cadence f which is then measured by a binary counter.