using analogue integrators, e.g. capacitors establishing a mean value by balance of input signals and defined discharge signals or leakage

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Arrangements for measuring frequencies; Arrangements for analysing frequency spectra > Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage > by converting frequency into an amplitude of current or voltage > using analogue integrators, e.g. capacitors establishing a mean value by balance of input signals and defined discharge signals or leakage