摘要 |
The invention relates to a subscriber circuit of a digital telephone exchang e with connectable subscriber lines (TL), said subscriber circuit consisting of a high-threshold part (HV) and a low threshold part (N V) containing a signal processor. According to the invention, test functions for testing the reliability performance of the subscriber circuit are integrated into the same using existing components and without placing a significant burden on the signal processor. The injection of an alternating current (S) produced by a tone generator (TOG) is followed by a frequency selective current threshold comparison by which means the reliability performance of the subscriber circuit can be determined rapidly.
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