| 摘要 |
A protection circuit for a DSL transceiver unit includes a capacitor connected in series between a first and second portion of a primary winding of a transformer. The first and second portions are coupled to first and second lines, respectively, of a twisted-pair telephone line. A first voltage controlled device is coupled to the first line and a chassis ground. The first voltage controlled device has a first threshold turn-on voltage at which the first voltage controlled device provides a first current path from the first line to chassis ground. A resistive device and a second voltage controlled device are coupled across the capacitor in series. The second voltage controlled device has a second threshold turn-on voltage at which the second voltage controlled device provides a second current path from a first capacitor terminal of the capacitor to a second capacitor terminal of the capacitor. The second threshold turn-on voltage is lower than the first threshold turn-on voltage.
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