| 摘要 |
A Digital Subscriber Line Access Multiplexer includes a set of line cards, a set of xDSL modem cards, a redundant xDSL modem card, a test and switching unit, a control unit, and a trunk unit. Each line card may include a switch, through which the control unit may selectively direct the line card to couple to a corresponding xDSL modem card or a redundancy bus. The test and switching unit is coupled to the redundancy bus, and includes a relay matrix and a Copper Loop Tester (CLT). In response to commands received from the control unit, the relay matrix may route redundancy bus signals to the CLT and/or the redundant xDSL modem card. The CLT performs tests to measure or determine subscriber loop electrical characteristics in response to control unit commands, and returns test results to the control unit.
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