| 摘要 |
In order to locate faults during the functional testing of a four-wire connection-individual switching device (R, E, DEC, D, S, ENC, E) and a four-wire line (U) connected to them, signals received via this line are compared with functional test signals if they are found to have errors. These test signals are supplied by a test device (Z) to the outgoing branch (y) of the relevant connection-individual switching device (R, E, DEC, D, S, ENC, E), then supplied via a rerouting device (R) provided in it, bypassing the four-wire line (U), to the incoming branch (x) of the connection-individual switching device (R, E, DEC, D, S, ENC, E), and are then received by means of their receivers (E, DEC, D, V). If the test with functional test signals results in the reception of signals having errors in the same manner, the fault location is in the connection-individual switching device (R, E, DEC, D, S, ENC, E), if not, it is located in the four-wire line (R, E, DEC, D, S, ENC, E) or the device (W) connected to its other end. <IMAGE>
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