| 摘要 |
The circuit checks the fault state of the line, terminal and circuit of the subscriber, and the analog relay line. It also checks whether the line is in use or not and provides the test tone to find out the fault position. It comprises an interface (10) interfacing between the subscriber and the exchange system, a test control unit (21), a testing circuit (22), a time switch (30), a microprocessor (40) being higher than the test control unit, and an operator station (50). The interface is connected to a test bus (A) for the subscriber line and a test bus (B) for the subscriber circuit.
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