| 摘要 |
A method for measuring the attenuation in digital transmission lines between a switching centre and a subscriber station, with a first pulse of a known frequency spectrum being sent from the switching centre to the transmission line. From the multitude of the reflections received by the switching centre in the time domain that pulse is selected which was caused by the total reflection at the end of the line of a certain subscriber station. The frequency spectr um of the selected pulse is determined and from the frequency spectra of the outgoing pulse and the selected received pulse, the attenuation of the transmission line is determined, depending on its frequency. To achieve the extremely high dynamics necessary for this and to obtain a pulse which is fr ee of any overshoot, reflection measuring is carried out selectively in the frequency range and the pulse is calculated per Fourier transformation. In order to reduce pulse widening by dispersion, the pulse in the frequency ran ge is shifted to higher frequencies. The method makes it possible to qualify subscriber stations for new services by measuring the attenuation from the switching centre.
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