| 摘要 |
Interface control circuit between three people in the two line telephone, consists of a voltage detecting means, an impedance interface means, the second and third bridge rectifier, the first and second amplifier and a microprocessor. The microprocessor detects the line voltage through the voltage detecting means, and controls the voltage detecting means and the impedance interface means according to the line voltage. The line A interfaces with the first bridge rectifier and the line B interfaces with the fourth bridge rectifier, or the line A interfaces with the second bridge rectifier and the line B interfaces with the third bridge rectifier.
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