摘要 |
An improved line interface device (300) and an improved xDSL modem (305) for use in connecting data communications equipment to a xDSL line is disclosed. The line interface device (300) provides the required isolation between the xDSL line and the communication equipment using optical isolation or capacitive techniques, the line interface device (300) also provides the power necessary to produce the transmit signal levels required by the communication service by utilizing a switching power supply (360) deriving its power from a source isolated from the line, and including a transformer (364) for isolating the source from the xDSL line. By switching at high frequencies the size of the transformer (364) can be sufficiently small so that of all the circuitry of the interface device (300) can be integrated in a small IC package.
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