METHOD FOR QUICKLY TESTING THE OPERABILITY OF A SUBSCRIBER CIRCUIT

Test functions to test an operability of a subscriber circuit are integrated in the subscriber circuit. The test functions use existing components and do not significantly burden the signal processor of the subscriber circuit. The subscriber circuit is provided in a digital telephone exchange having connectable subscriber lines and has a high-voltage section and a low-voltage section. Once an alternating current, which is produced by a tone generator, has been fed into connecting paths, a frequency-selective current threshold-value comparison is carried out, by which the operability of the subscriber circuit can quickly be confirmed.