| 摘要 |
<p>Prior art circuits for determining the frequency response of a unit under test comprise a VCO and e.g. a cathode ray tube on which the respective spectrum from the unit under test is displayed. For accurate allocation between wobble frequency and spectral amplitude, the VCO had to be periodically calibrated. For simplification purposes, the invention provides a counter which either counts quartz-stabilized pulses during a VCO period or which counts, during a quartz-stablized counting interval, the VCO output pulses themselves. The counts represent with quartz accuracy the test frequency, which corresponds to the mean value within the counting interval.</p> |
