Abstract: The test specimen is charged with an analog, preferably sinusoidal periodic test signal or, respectively, with the digital samples of such a test signal, whereby a numerical relationship exists between the period of the test signal and the system-inherent sampling period such that all sampling times lying within a predetermined test time span occupy different relative time slots in the periodicity interval of the test signal. Arising as a result thereof are a plurality of output information of the test specimen which, as a totality, describe the response of the test specimen to the test signal as precisely as desired. Said output information are, if need be after analog-to-digital conversion in a standard coder, deposited in a store and are available for identifying the desired properties of the test specimen, for example, the level-dependent distortions, by means of a computer.