| 摘要 |
Method and apparatus for selecting a single telephone line from among multiple line pairs at a location remote from the central office and isolating that line from the respective subscriber line to allow the performance of line tests on same. Line pairs are sampled sequentially for a short time interval to determine whether a signal is present within an initial detection band, that band having a range about +/-100 hz of the test signal frequency. If a signal is found, the system shifts to a validation made to defect a signal within a range of about +/-10 hz of the test signal frequency during a preselected long time interval. Upon finding a signal present at the end of the validation cycle, the system disconnects the selected line from its respective subscriber line and begins performing line tests to diagnose problems.
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